(American football, Canadian football) a quarterback

Alternative form of クォーターバック (kwōtābakku, “quarterback”)

(baseball) backstop

backrooms (of a store)

backlash (a strong adverse reaction to a political or social development)

backsword

(dated slang) a woman who is attractive from behind, usually in reference to her buttocks. / (dated slang, in particular) butterface: A woman who is attractive from behind but ugly from the front.

illegitimacy (being born out of wedlock)

a privately-owned ricefield, especially one under the historical 律令 (Ritsuryō) system

Kyūjitai form of 私鉄 (“private railway”)