A small amount of prepubescent facial hair appearing on the upperlip on males ages 10-16. This can usually only be seen on boys with dark hair. Sometimes boys think this look cool and decide not to shave it off. Not be confused with frenchman
Man, Joey. Your teen-stache makes your look like a frenchman.
A portmanteau describing a teenager's moustache that ranges from faint to very noticeable, but never thick enough to look even remotely good. It remains until the person shaves for the first time.
That guy has such a teenstache, I wish he'd buy a razor.