Moo \Moo\, a., adv., & n. See Mo. [Obs.]

--Chaucer.

Source: Webster's Revised Unabridged Dictionary (1913)
 

Moo \Moo\, v. i. [imp. & p. p. Mooed; p. pr. & vb. n. Mooing.]

[Of imitative origin.]

To make the noise of a cow; to low; -- child's word.

Source: Webster's Revised Unabridged Dictionary (1913)
 

Moo \Moo\, n. The lowing of a cow.

Source: Webster's Revised Unabridged Dictionary (1913)