Meaning of “back” - Learner’s Dictionary

back

adverb uk us /bæk/
RETURNING

A1 where someone or something was before:

I'll be back in Sydney on the 20th.
When do you go back to college?
I put it back in the cupboard.
BEHIND

B1 in a direction behind you:

Anna stepped back.
Flint leaned back in his chair.
REPLY

A2 as a reply or reaction to something:

UK to ring back/ US to call back
I signalled to her and she waved back.
STATE

B1 to the state something or someone was in before:

Hopefully things will get back to normal again now.
I'm sure we can put it back together again (= repair it).
Try to go back to sleep.
EARLIER

B2 at or to an earlier time:

We first met back in 1973.
Looking back, I think we did the right thing.
AWAY FROM

B2 in a direction away from something:

He pulled back the curtain.
The house was a short distance back from the road.
back and forth (also backwards and forwards)

in one direction, then the opposite way, then in the original direction again many times:

He has to travel back and forth between London and Paris every week.

(Definition of “back adverb” from the Cambridge Learner’s Dictionary © Cambridge University Press)