preposition

At or to the far side of (something), typically so as to be hidden by it.

the recording machinery was kept behind screens

at the back of,at the rear of,beyond,on the other side of,on the far side of,on the further side of

adverb

At or to the far side or the back side of something.

Campbell grabbed him from behind

noun

The buttocks.

buttocks,bottom,cheeks,hindquarters,haunches,rump,rear end,seat