Letters that make keep mum
e, k, p, m, u are letters that make 'keep mum'
1 possible definitions for 'keep mum'
Under this definition, keep mum is a verb and has the following properties:
dummy up, belt up, button up, be quiet, shut up, close up, clam up have the same meaning as 'keep mum'
open up has the opposite meaning of keep mum