Whistling
noun
A mouth flute... Normal flutes you blow air through to make a sound. How do you blow air through your mouth to make a sound? By whistling.
The reading is the kun'yomi readings put together. Thank 口 for being a body part, which tends to cause this to happen. So, you have 口 (くち) and 笛 (ふえ) put together, though ふえ changes to ぶえ, maybe because you can't whistle properly? Buuuweeee. Buwwweee.
その男の子は、うれしそうに口笛をふいていました。
That boy was whistling happily.
夜おそくまでオフィスにいると、よく上司が口笛の練習をしている音が聞こえてくる。
I frequently hear the sound of my boss practicing his whistling when I'm at the office late at night.
口笛が下手くそなので、私が口笛を吹いても犬が来てくれません。
My dog doesn’t come to my whistle because I’m bad at whistling.