Webster's Revised Unabridged Dictionary · 1913

Baa

Baa (ba) , intransitive verb

[Compare German baen; an imitative word.]

To cry baa, or bleat as a sheep.
He treble baas for help, but none can get. — Sir P. Sidney

Baa (ba) , noun

[Compare German ba.]

The cry or bleating of a sheep; a bleat.