"he wrote on the flap of the envelope"
"he was in a dither"
"there was a terrible flap about the theft"
"The curtains undulated"
"the waves rolled towards the beach"
"flags flapped in the strong wind"
"The bird flapped its wings"
"The eagle beat its wings and soared high into the sky"
"The bird's wings were flapping"
The goose flapped heavily away.
那只鹅笨重地拍翅跑开了。
flap sth ⇔ awayHe flapped the flies away with a fan.
他用扇子把苍蝇拍走。