A back issue of a magazine, etc. / Anything considered old-fashioned.

(figuratively) Of work, very physically tiring.

Alternative spelling of back-formation.

A person who says nasty things about another person behind the second person's back: that is, out of their sight and hearing.

Used other than figuratively or idiomatically: see back, into. / (sports, idiomatic) To advance to the post-season as a result of another team's loss, especially where one's own team has also lost.

From one place to another and back again.

Going from one place or position to another and back again.

The movement (of someone or something) forward followed by a return to the same position. May refer to a concept such as an emotional state or a relationship as well as a physical thing.

a passerine bird of the antbird family, Sakesphorus melanonotus.

a passerine bird of the antbird family, Hypoedaleus guttatus.