Butt ugly

A perjorative term for someone so ugly, so exceedingly unattractive. that he or she is as "ugly as a butt" (a misnomer, since many buttocks are beautiful indeed). A popular teen-age slang term since the 80s, "butt-ugly" most probably began as military slang c. World War II. Probably because enlisted men found nothing attractive about another enlisted man's hairy, sweaty, very possibly pimpled butt!