Definition of outcrop

i. The part of a rock formation that appears at the surface of the ground.

Ref: Webster 3rd

ii. A term used in connection with a vein or lode as an essential part of the definition of apex. It does not necessarily imply the visible presentation of the mineral on the surface of the earth, but includes those deposits that are so near to the surface as to be found easily by digging.

Ref: Fay

iii. The part of a geologic formation or structure that appears at the surface of the Earth; also, bedrock that is covered only by surficial deposits such as alluvium.

Compare with: exposure, outcropping

Ref: AGI

iv. To appear exposed and visible at the Earth's surface; to crop out.

Ref: AGI