bimbo; airhead beauty
A derogatory term for a woman whose attractiveness is seen as her only quality, implying lack of intelligence. Sensitive and potentially offensive; used in casual or critical contexts.
Some people say she's just a bimbo, but she's actually very smart.
The heroine of that movie is portrayed as an airhead beauty.
バカ means 'fool' or 'idiot' and can be used for anyone, while 白痴美 specifically targets a woman's appearance combined with perceived stupidity.
Compound of 白痴 (はくち, 'idiocy') and 美 (び, 'beauty'). The exact origin is uncertain, but it likely emerged as a slang term in modern Japanese.