Deep  —adj. 1 extending far down or in (deep water; deep wound; deep shelf). 2 (predic.) A to or at a specified depth (water 6 feet deep). B in a specified number of ranks (soldiers drawn up six deep). 3 situated or coming from far down, back, or in (deep in his pockets; deep sigh). 4 low-pitched, full-toned (deep voice). 5 intense, extreme (deep sleep; deep colour; deep interest). 6 (predic.) Fully absorbed or overwhelmed (deep in a book; deep in debt). 7 profound; difficult to understand (too deep for me). —n. 1 (prec. By the) poet. Sea, esp. When deep. 2 abyss, pit, cavity. 3 (prec. By the) cricket position of a fielder distant from the batsman. 4 deep state (deep of the night). —adv. Deeply; far down or in (dig deep).  go off the deep end colloq. Give way to anger or emotion. In deep water in trouble or difficulty.  deeply adv. [old english]