a friendly greeting in which you touch someone's fist (= closed hand) with your own fist

His fans greeted him with fistbumps of congratulation. 他的球迷们跟他击拳庆祝胜利。

to greet someone in a friendly way by touching their fist with your own fist

If I saw him I'd walk up to him and fistbump him. 如果我看见他，就会走上前去击拳问好。