mum

nouns

of China
Chrysanthemum morifolium, Dendranthema grandifloruom, florist's chrysanthemum, florists' chrysanthemum, mum
informal terms for a mother
ma, mama, mamma, mammy, mom, momma, mommy, mum, mummy
secrecy
"mum's the word"
mum
is a type of (narrower)
the trait of keeping things secret
secrecy, secretiveness, silence

adjectives

failing to speak or communicate etc when expected to
"the witness remained silent"
mum, silent