expression, godan verb (-ku)
Idiomatic expression literally meaning 'to pull buttock hair', used figuratively for catching someone off guard or startling them unexpectedly.
いきなり後ろから声をかけられて、尻毛を抜かれたよ。
I was startled when someone suddenly called out to me from behind.
彼の突然の告白には、本当に尻毛を抜かれた。
His sudden confession really took me by surprise.