Real Dictionary

moth
countable noun: A moth is an insect like a butterfly which usually flies about at night.

moth in American English
any of various families of chiefly night-flying lepidopteran insects, similar to the butterflies but generally smaller, less brightly colored, and not having the antennae knobbed
noun: any of numerous insects of the order Lepidoptera, generally distinguished from the butterflies by having feathery antennae and by having crepuscular or nocturnal habits

moth in British English
noun: any of numerous insects of the order Lepidoptera that typically have stout bodies with antennae of various shapes (but not clubbed), including large brightly coloured species, such as hawk moths, and small inconspicuous types, such as the clothes moths