Definition of back :
1. ( Of time) In times past; ago.
2. A ferryboat. See Bac, 1.
3. A garment for the back; hence, clothing.
4. A large shallow vat; a cistern, tub, or trough, used by brewers, distillers, dyers, picklers, gluemakers, and others, for mixing or cooling wort, holding water, hot glue, etc.
5. A support or resource in reserve.
6. An extended upper part, as of a mountain or ridge.
7. Away from contact; by reverse movement.
8. Being at the back or in the rear; distant; remote; as, the back door; back settlements.
9. Being in arrear; overdue; as, back rent.
10. In a state of restraint or hindrance.
11. In arrear; as, to be back in one's rent.
12. In concealment or reserve; in one's own possession; as, to keep back the truth; to keep back part of the money due to another.
13. In human beings, the hinder part of the body, extending from the neck to the end of the spine; in other animals, that part of the body which corresponds most nearly to such part of a human being; as, the back of a horse, fish, or lobster.
14. In return, repayment, or requital.
15. In withdrawal from a statement, promise, or undertaking; as, he took back0 the offensive words.
16. In, to, or toward, the rear; as, to stand back; to step back.
17. Moving or operating backward; as, back action.
18. The keel and keelson of a ship.
19. The outward or upper part of a thing, as opposed to the inner or lower part; as, the back of the hand, the back of the foot, the back of a hand rail.
20. The part of a cutting tool on the opposite side from its edge; as, the back of a knife, or of a saw.
21. The part opposed to the front; the hinder or rear part of a thing; as, the back of a book; the back of an army; the back of a chimney.
22. The part opposite to, or most remote from, that which fronts the speaker or actor; or the part out of sight, or not generally seen; as, the back of an island, of a hill, or of a village.
23. The upper part of a lode, or the roof of a horizontal underground passage.
24. To a former state, condition, or station; as, to go back to private life; to go back to barbarism.
25. To adjoin behind; to be at the back of.
26. To bet on the success of; - as, to back a race horse.
27. To change from one quarter to another by a course opposite to that of the sun; - used of the wind.
28. To drive or force backward; to cause to retreat or recede; as, to back oxen.
29. To get upon the back of; to mount.
30. To make a back for; to furnish with a back; as, to back books.
31. To move or go backward; as, the horse refuses to back.
32. To place or seat upon the back.
33. To stand still behind another dog which has pointed; - said of a dog.
34. To support; to maintain; to second or strengthen by aid or influence; as, to back a friend.
35. To the place from which one came; to the place or person from which something is taken or derived; as, to go back for something left behind; to go back to one's native place; to put a book back after reading it.
36. To write upon the back of; as, to back a letter; to indorse; as, to back a note or legal document.
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assist (part of speech: verb)
rear (part of speech: noun)
at the heels of, seat, aback, after, fanny, hinder, in the wake, caudal, behind, final, caboose, astern, in back of, backside, abaft, in the wake of, in the background, terminal, to or in the rear, derriere, stern, dorsal, hind, aft, following, rump
support (part of speech: verb)
back (part of speech: noun)