1
general::
Phrase(s): *bald as a coot [and] *bald as a baby’s backside
completely bald. (*Also: as ~.) • If Tom’s hair keeps receding like that, he’ll be bald as a coot by the time he’s thirty. • Fred: Now, I’ll admit my hair is thinning a little on the top, but— Jane: Thinning? You’re not thinning, you’re as bald as a baby’s backside!
McGrawhill's American Idioms And Phrasal Verbs