also: ばたあし · バタアシ
noun
flutter kick
A basic swimming kick where the legs move up and down alternately; often the first kick taught to beginners. The English gloss 'the thrash' is a less common variant.
水泳の授業で、まずバタ足の練習をした。
In swimming class, we first practiced the flutter kick.
バタ足が上手にできるようになると、クロールが楽になる。
Once you can do the flutter kick well, the front crawl becomes easier.
Hiragana mimetic with 脚; rarely used.
From the mimetic word バタバタ (splashing, flapping) and 足 (foot/leg), describing the splashing motion of the feet in the water.