back / a backer, a supporter (someone who supports a person or enterprise) / reversing, moving backwards

(sex); go back / move backwards / give a refund

back / reverse / rear / support / background

of a song, in full

a target, a mark, a bullseye / an objective, an object (of doing something)

as far as ... is concerned; in terms of ...

a song; to sing / Japanese poetry; waka

song; sing

(Internet slang) Abbreviation of ブルーバック.

play dumb, feign ignorance / (slang) evade one's responsibilities, especially by failing to appear to perform a duty