Definition of spot-check:
(n) :
A round or irregular patch on the surface of a thing having a different color, texture etc. and generally round in shape.
(n) :
A stain or disfiguring mark.
(n) :
A pimple, papule or pustule.
(n) :
A symbol on a playing card, domino, die, etc. indicating its value; a pip.
(n) :
A small, unspecified amount or quantity.
(n) :
(slang, US) A bill of five-dollar or ten-dollar denomination in dollars.