"mum's the word"
"the witness remained silent"
Don't stand there mum.
UH head football coach..was mum on a successor.
He has decided to be mum on this matter.
The Mum restricts her son-in-law's roles.
The pre-school children of the young mums were taking part in a nursery.
牛津高阶第八版
美国韦氏词典
Dictionary.com
Free Dictionary
维基百科 (自由的百科全书)