having great spatial extension or penetration downward or inward from an outer surface or backward or laterally or outward from a center; sometimes used in combination(adj.all)
Example:
A deep well.
A deep dive.
Deep water.
A deep casserole.
A deep gash.
Deep massage.
Deep pressure receptors in muscles.
Deep shelves.
A deep closet.
Surrounded by a deep yard.
Hit the ball to deep center field.
In deep space.
Waist-deep.
source: wordnet30