They are clapping their hands.

他们在拍手。

youdao

People are clapping, slapping their thighs, stomping the floor.

人们鼓掌，拍着大腿，跺着地板。

youdao

The high school girls have stopped their clapping game and are pretending to speak in Spanish between laughing fits.

那几个玩拍手游戏的高中女孩挺了下来，尝试着说一阵西班牙语。

youdao

Our other swimmers are still undressing, but the two of us are jumping and clapping and calling them in.

WSJ: Cold-Water Swimming in Alaska

Classical-music audiences, for instance, tend to be mostly quiet and strikingly attentive, but also a bit inhibited, perhaps because many of the people who come to concerts are afraid of clapping at the wrong time.

WSJ: Theatergoers: Can I Get an Amen? | Sightings by Terry Teachout

Discipline is strict, but classes are livened up with clapping and chanting--"Read, baby, read!"

FORBES: Magazine Article