Finely trimmed pubic hair on a man or a woman.
Your mother's skirt was so short I could see her australian mustache.
by Capt. Morgan March 09, 2007
1 more definition
(n): The result of growing a mustache with your pubes "down under".
Your Australian mustache is really tickling my nose.
by Falkor the Ghost Puncher January 19, 2011