say it: MUH-stash
moustache is a noun meaning "an unshaved growth of hair on the upper lip". It carries one recorded sense.
an unshaved growth of hair on the upper lip
“he looked younger after he shaved off his mustache”
Forms marked · are formed by the regular rule rather than recorded in the source data. English keeps a few hundred irregulars and the rest follow the pattern, so the rule is right far more often than not — but it is a rule, and the mark says so.
Definitions, synonyms and semantic relations for moustache come from Princeton University’s WordNet. The pronunciation comes from the CMU Pronouncing Dictionary. Commonness is measured against a corpus of everyday English. Full sources and licences.