mum
1. mum \'m*m\ aj [prob. imit. of a sound made with closed lips] : SILENT
{keep ~} - often used interjectionally
2. mum vt or mummed; or mum.ming [ME mommen, fr. MF momer to go masked] 1:
to act or play usu. in mask or disguise 2: to go about merrymaking in
disguise during festivals
3. mum n [G mumme] : a strong ale or beer
4. mum n : CHRYSANTHEMUM
Webster's English Dictionary