Wiktionary
n. A swimming stroke in which the body is prone, the arms are moved in simultaneous circles, and the feet are kicked up and down.
WordNet
n. a swimming stroke in which the arms are thrown forward together out of the water while the feet kick up and down [syn: butterfly]
Wikipedia
The butterfly (colloquially shortened to the ''fly'') is a swimming stroke swum on the breast, with both arms moving simultaneously, accompanied by the butterfly kick (also known as the "dolphin kick"). While other styles like the breaststroke, front crawl, or backstroke can be swum adequately by beginners, the butterfly is a more difficult stroke that requires good technique as well as strong muscles. It is the newest swimming style swum in competition, first swum in 1933 and originating out of breaststroke.
Usage examples of "butterfly stroke".
Using a butterfly stroke, making all the speed he could, he headed straight for the mighty facade of the temple, marveling at the power he could summon from his new shoulders.
A butterfly stroke carried her to the small flat circle that marked the intersection of two spheres.