baa       
noun [ C ] uk/bɑː/ us/bæ/
 羊的叫声
the sound that a sheep or goat makes
  "Baa," bleated the sheep.
 We listened to the therapeutic baas of sheep coming from the hills.
 - More examples
 - "Baa," say the sheep.
 - A child may hear the sheep puppet say "baa".
 - Sheep go baa, ducks go quack.