adjective

1. extending far downward from the top or top edges, inward from the surface, or backward from the front a deep cut, a deep lake, a deep drawer
2. extending down, inward, etc. a specified length or distance water eight feet deep
3. 1. located far down or back deep in the outfield
   2. coming from or going far down or back a deep breath
4. far off in time or space the deep past
5. hard to understand; abstruse a deep book
6. extremely grave or serious in deep trouble
7. strongly felt deep love
8. intellectually profound a deep discussion
9. 1. tricky and sly; devious deep dealings
   2. carefully guarded a deep secret
10. dark and rich a deep red
11. sunk in or absorbed by: with in deep in thought
12. 1. great in degree; intense deep joy
    2. heavy and unbroken a deep sleep
13. much involved deep in debt
14. of low pitch or range a deep voice
15. large; big deep cuts in the budget
16. Sports having many good players in reserve a team deep in pitching

Etymology: ME dep < OE deop, akin to Ger tief, Goth diups < IE base *dheub-, deep, hollow > dip, dump

noun

1. a deep place or any of the deepest parts, as in water or earth
2. the extent of encompassing space or time, of the unknown, etc.
3. the middle part; part that is darkest, most silent, etc. in the deep of night
4. Naut. any of the unmarked fathom points between those marked on a lead line

Etymology: ME dep < OE deop

adverb

Etymology: ME depe < OE deope