noun / verb / interjection
moo
MOO/mˈu/
The characteristic low sound of cattle, or making that sound.
The cow raises its head and gives a moo.

Etymology
Moo arose as an imitation of a cow’s characteristic call. Its meaning comes directly from the sound it imitates, rather than from identifiable ancestral components.
In context
I like to quack like a duck, or moo like a cow.