Some young men were cat-calling at girls passing by on the street, which was very rude.

cat-calling 是由 cat（猫）和 calling（叫喊）组成的复合词。cat 在这里比喻像猫叫一样轻浮的声音，calling 指"喊叫"。 cat-calling 指在公共场合对异性发出轻浮的口哨声或调戏性言语的行为，通常带有性骚扰性质。这种行为被认为是不礼貌且冒犯的。