WordReference Random House Unabridged Dictionary of American English © 2026
deep•ly
(dēp′lē),USA pronunciation adv.
WordReference Random House Learner's Dictionary of American English © 2026- at or to a considerable extent downward;
well within or beneath a surface. - to a thorough extent or profound degree:deeply pained; deeply committed.
- with depth of color, tone, sound, etc.
- with great cunning, skill, and subtlety.
- Middle English deply, Old English dēoplīce, derivative of dēoplīc (adjective, adjectival), equivalent. to dēop deep + -līc(e) -ly bef. 900
- 2. greatly, thoroughly, intensely, acutely.
deep /dip/USA pronunciation
adj. and adv., -er, -est, n.
adj.
adv.
n. [uncountable]
deep•ly, adv.
deep•ness, n. [uncountable]
WordReference Random House Unabridged Dictionary of American English © 2026adj.
- extending far down from the top or surface:a deep well.
- extending far in or back from the front:a deep shelf.
- extending far in width;
broad:a deep border. - [after a noun indicating measurement] having a certain specified dimension or amount in depth:a tank 10 feet deep.
- [~ + in] immersed or submerged:The road was deep in snow.
- [before a noun] coming from far down:Now, take a deep breath.
- made with the body bent or lowered to a considerable degree:a deep curtsy.
- difficult to understand;
abstruse;
a book too deep for young children. - not superficial;
serious;
profound:deep thoughts. - [before a noun] sincere;
intense;
great:deep affections. - [before a noun] sound and heavy;
undisturbed:deep sleep. - strong, dark, and vivid in color:a deep red.
- low in pitch, such as sound:a deep, rich voice.
- mysterious;
hidden:deep secrets. - [ ~ + in] involved to a great extent:to be deep in debt.
- giving one's full attention;
absorbed;
engrossed:[be + ~ + in]He was deep in thought.
adv.
- to or at a considerable or great depth:We were about ten feet deep when our ears popped.
- [after a number, noun, or adjective indicating measurement] to a depth or breadth of (the number, noun, or adjective mentioned):The fans were lined up three deep around the block.
- far on in time;
late:They worked deep into the night. - within;
far down:I still feel love for her deep in my heart.
n. [uncountable]
- [ often: the + ~ + of] the midpoint or the part of greatest intensity:the deep of winter; in the deep of the night.
- the deep, [Literary.]the sea or ocean:The deep was the drowned sailor's final resting place.
- Idioms go off the deep end:
- to become emotionally overwrought:She went off the deep end when she was turned down for promotion.
- to act without enough thought of the consequences:The committee went off the deep end with the Christmas decorations.
- Idioms in deep, involved:He was in too deep with her and had to break off their relationship.
- Idioms in deep water, in serious trouble:The company is in deep water and can barely make ends meet.
deep•ly, adv.
deep•ness, n. [uncountable]
deep
(dēp),USA pronunciation adj. -er, -est, n., adv., -er, -est.
adj.
n.
adv.
deep′ness, n.
adj.
- extending far down from the top or surface:a deep well; a deep valley.
- extending far in or back from the front or from an edge, surface, opening, etc., considered as the front:a deep shelf.
- extending far in width;
broad:deep lace; a deep border. - ranging far from the earth and sun:a deep space probe.
- having a specified dimension in depth:a tank 8 feet deep.
- covered or immersed to a specified depth (often used in combination):standing knee-deep in water.
- having a specified width or number of items from front to back (often used in combination):shelves that are 10 inches deep; cars lined up at the entrance gates three-deep.
- extending or cutting far down relative to the surface of a given object:The knife made a deep scar in the table.
- situated far down, in, or back:deep below the surface; deep in the woods.
- reaching or advancing far down:a deep dive.
- coming from far down:a deep breath.
- made with the body bent or lowered to a considerable degree:a deep bow.
- immersed or submerged in or heavily covered with (fol. by in):a road deep in mud.
- difficult to penetrate or understand;
abstruse:a deep allegory. - not superficial;
profound:deep thoughts. - grave or serious:deep disgrace.
- heartfelt;
sincere:deep affections. - absorbing;
engrossing:deep study. - great in measure;
intense;
extreme:deep sorrow. - sound and heavy;
profound:deep sleep. - (of colors) dark and vivid:a deep red.
- low in pitch, as sound, a voice, or the like:deep, sonorous tones.
- having penetrating intellectual powers:a deep scholar.
- profoundly cunning or artful:a deep and crafty scheme.
- mysterious;
obscure:deep, dark secrets. - immersed or involved;
enveloped:a man deep in debt. - absorbed;
engrossed:deep in thought. - Sport[Baseball.]relatively far from home plate:He hit the ball into deep center field.
- Linguisticsbelonging to an early stage in the transformational derivation of a sentence;
belonging to the deep structure. - Idioms go off the deep end:
- to enter upon a course of action with heedless or irresponsible indifference to consequences.
- to become emotionally overwrought.
- Idioms in deep water:
- in difficult or serious circumstances;
in trouble. - in a situation beyond the range of one's capability or skill:You're a good student, but you'll be in deep water in medical school.
- in difficult or serious circumstances;
n.
- Geology, Oceanographythe deep part of a body of water, esp. an area of the ocean floor having a depth greater than 18,000 ft. (5400 m).
- a vast extent, as of space or time.
- the part of greatest intensity, as of winter.
- Nautical, Naval Termsany of the unmarked levels, one fathom apart, on a deep-sea lead line. Cf. mark1 (def. 20).
- the deep, [Chiefly Literary.]the sea or ocean:He was laid to rest in the deep.
adv.
- to or at a considerable or specified depth:The boat rode deep in the water.
- far on in time:He claimed he could see deep into the future.
- profoundly;
intensely. - Sport[Baseball.]at or to a deep place or position:The outfielders played deep, knowing the batter's reputation as a slugger.
- Idioms in deep:
- inextricably involved.
- having made or committed oneself to make a large financial investment.
- bef. 900; Middle English dep, Old English dēop; akin to Gothic diups, Old Norse djupr, Old High German tiof
- 14. recondite, mysterious, obscure, profound. 23. sagacious, wise, profound, shrewd.
- 1. 10. 15. –17, 23. shallow.
'deeply' also found in these entries (note: many are not synonyms or translations):
absorbed
- adore
- affected
- Arminian
- assume
- badlands
- belly
- brown
- burrow
- cogitate
- comb
- Cornwall
- crab
- cut up
- dandelion
- deep-set
- deliberate
- delve
- devout
- ear
- elbow
- embed
- engrave
- fast
- fatsia
- feel
- Galway
- heart
- heartsick
- hemp
- hollow
- home
- immerse
- inbred
- ingrain
- ingrained
- inquisition
- inquisitor
- insight
- intimate
- Kerry
- knee-deep
- know
- mackerel
- meditate
- Moorish idol
- nightmare
- Norway
- pecan
- absorbing