loachPronunciation: /ləʊtʃ/Definition of loach noun a small elongated bottom-dwelling freshwater fish with several barbels near the mouth, found in Eurasia and NW Africa. Family Cobitidae and Homalopteridae (or Balitoridae): several genera and numerous species Origin: Middle English: from Old French loche, of unknown originloach in other Oxford dictionaries Definition of loach in the US English dictionary