open one's mouth

open wide

To open one's mouth wide, to gape.

mouth the words

To speak insincerely.

catch flies

To have one's mouth wide open for a prolonged period.

put the bad mouth on

To speak ill of; to vilify.

get wind in one's jaws

To have too much to say; talk too much; run at the mouth; to speak one…

run at the mouth

To speak ceaselessly or without end.