Adverb
Verb (する)
Onomatopoeic
1. fluttering; flapping; waving
ひらひらと、いつまでも桜は降る。The cherry blossoms flutter down endlessly.
2. flickering (light, flame, etc.)
3. frill; piece of thin material
このドレスは袖のひらひらがかわいい。The frills on the sleeves of this dress are cute.