The Collaborative International Dictionary of English v.0.48:
Deep \Deep\ (d[=e]p), a. [Compar. Deeper (d[=e]p"[~e]r);
superl. Deepest (d[=e]p"[e^]st).] [OE. dep, deop, AS.
de['o]p; akin to D. diep, G. tief, Icel. dj[=u]pr, Sw. diup,
Dan. dyb, Goth. diups; fr. the root of E. dip, dive. See
1. Extending far below the surface; of great perpendicular
dimension (measured from the surface downward, and
distinguished from high, which is measured upward); far to
the bottom; having a certain depth; as, a deep sea.
The water where the brook is deep. --Shak.
2. Extending far back from the front or outer part; of great
horizontal dimension (measured backward from the front or
nearer part, mouth, etc.); as, a deep cave or recess or
wound; a gallery ten seats deep; a company of soldiers six
Shadowing squadrons deep. --Milton.
Safely in harbor
Is the king's ship in the deep nook. --Shak.
3. Low in situation; lying far below the general surface; as,
a deep valley.
4. Hard to penetrate or comprehend; profound; -- opposed to
shallow or superficial; intricate; mysterious; not
obvious; obscure; as, a deep subject or plot.
Speculations high or deep. --Milton.
A question deep almost as the mystery of life. --De
O Lord, . . . thy thoughts are very deep. --Ps.
5. Of penetrating or far-reaching intellect; not superficial;
thoroughly skilled; sagacious; cunning.
Deep clerks she dumbs. --Shak.
6. Profound; thorough; complete; unmixed; intense; heavy;
heartfelt; as, deep distress; deep melancholy; deep
horror. "Deep despair." --Milton. "Deep silence."
--Milton. "Deep sleep." --Gen. ii. 21. "Deeper darkness."
--Hoole. "Their deep poverty." --2 Cor. viii. 2.
An attitude of deep respect. --Motley.
7. Strongly colored; dark; intense; not light or thin; as,
deep blue or crimson.
8. Of low tone; full-toned; not high or sharp; grave; heavy.
"The deep thunder." --Byron.
The bass of heaven's deep organ. --Milton.
9. Muddy; boggy; sandy; -- said of roads. --Chaucer.
The ways in that vale were very deep. --Clarendon.
A deep line of operations (Military), a long line.
Deep mourning (Costume), mourning complete and strongly
marked, the garments being not only all black, but also
composed of lusterless materials and of such fashion as is
identified with mourning garments.