behind (adv., prep.)

Old English behindan "at the back of, after," from bi "by" (see by) + hindan "from behind" (see hind (adj.)). The prepositional sense emerged in Old English. Figurative sense "not so far advanced, not on equality with" is from c. 1200. Euphemistic noun meaning "backside of a person" is from 1786. To do something behind (someone's) back "clandestinely" is from late 14c. Phrase behind the times is by 1826. Behind the scenes (1711) is from the theater; figurative sense attested by 1779.

Definitions of behind
behind (adv.)
in or to or toward the rear;
the final runners were far behind
seen from behind, the house is more imposing than it is from the front
he followed behind
behind (adv.)
remaining in a place or condition that has been left or departed from;
he took off with a squeal of tires and left the other cars far behind
left a large family behind
when he died he left much unfinished work behind
the children left their books behind
behind (adv.)
of timepieces;
my watch is running behind
Synonyms: slow
behind (adv.)
in or into an inferior position;
their business was lagging behind in the competition for customers
fell behind in his studies
behind (adv.)
in debt;
a month behind in the rent
he fell behind with his mortgage payments
Synonyms: behindhand / in arrears
behind (n.)
the fleshy part of the human body that you sit on;
Synonyms: buttocks / nates / arse / butt / backside / bum / buns / can / fundament / hindquarters / hind end / keister / posterior / prat / rear / rear end / rump / stern / seat / tail / tail end / tooshie / tush / bottom / derriere / fanny / ass
behind (adj.)
having the lower score or lagging position in a contest;
behind by two points