Definition of "loach"

A bottom-feeding freshwater fish in the superfamily or suborder Cobitoidea.

1. Any true loach, of the family Cobitidae.  examples

2. A similar fish in one of three other families of Cypriniformes: Botiidae, Balitoridae, and Gyrinocheilidae.  examples

(slang) Synonym of LOH (light observation helicopter)