moo

1. V-I When cattle, especially cows, moo, they make the long, low sound that cattle typically make. (牛)哞哞叫

...a sound like a cow mooing. ...听起来像牛哞哞叫的声音。

2. N-COUNT/SOUND Moo is also a noun. (牛的)哞哞叫声

The cow says "moo-moo."

奶牛“哞哞”叫。