/ ˈbʌtəflaɪ; NAmE -tərf-/ noun ( pl. -ies )
1.
[ C ] a flying insect with a long thin body and four large, usually brightly coloured, wings :
butterflies and moths
She's like a butterfly. She flits in and out of people's lives.
2.
[ U ] a swimming stroke in which you swim on your front and lift both arms forward at the same time while your legs move up and down together :
She was third in the 200m butterfly (= a swimming race) .
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IDIOMS
- have butterflies (in your stomach)
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WORD ORIGIN
Old English , from butter + the insect fly ; perhaps from the cream or yellow colour of common species, or from an old belief that the insects stole butter.