n Any small fish.
n The common minnow (Phoxinus phoxinus), a small freshwater fish of the carp family Cyprinidae which has a green back with black elongated blotches, commonly swimming in large shoals.
n Chiefly with a qualifying word: any of a number of other (small) fish from the family Cyprinidae; also (chiefly US), other small (usually freshwater) fish from other families.
n (Australia, New Zealand) Synonym of galaxiid (“any member of the family Galaxiidae of mostly small freshwater fish of the Southern Hemisphere”); specifically, the common galaxias, inanga, or jollytail (Galaxias maculatus).
n (Britain, regional) Synonym of stickleback (family Gasterosteidae).
n (figuratively) A person or thing of relatively little consequence, importance, or value.
n (fishing) An artificial bait in the form of a small fish.
adj (rare) Very small; tiny.
v To fish for minnows (noun sense 1 and subsenses).
v To fish, especially for trout, using minnows as bait.