back¹ (băk)

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[Middle English bak, from Old English bæc.]

noun 

1. 1. The posterior portion of the trunk of the human body between the neck and the pelvis; the dorsum.
   2. The analogous dorsal region in other animals.
2. The backbone or spine.
3. The part or area farthest from the front.
4. The part opposite to or behind that adapted for view or use: the back of the hand; wrote on the back of the photograph.
5. The reverse side, as of a coin.
6. A part that supports or strengthens from the rear: the back of a couch.
7. 1. The part of a book where the pages are stitched or glued together into the binding.
   2. The binding itself.
8. Sports
   1. A player who takes a position behind the front line of other players in certain games, such as football and soccer.
   2. This playing position.

verb: backed, back·ing, backs. 

transitive verb 

1. To cause to move backward or in a reverse direction: Back the car up and then make the turn.
2. To furnish or strengthen with a back or backing.
3. To provide with financial or moral support; support or endorse: Unions backed the pro-labor candidate. See synonyms at support
4. To provide with musical accompaniment. Often used with up.
5. To bet or wager on.
6. To adduce evidence in support of; substantiate: backed the argument with facts.
7. To form the back or background of: Snowcapped mountains back the village.

intransitive verb 

1. To move backward: backed out of the garage.
2. To shift to a counterclockwise direction. Used of the wind.

adjective 

1. Located or placed in the rear: Deliveries should be made at the back entrance.
2. Distant from a center of activity; remote.
3. Of a past date; not current: a back issue of a periodical.
4. Being owed or due from an earlier time; in arrears: back pay.
5. Being in a backward direction.
6. Linguistics Pronounced with the back of the tongue, as oo in cool. Used of vowels.

adverb 

1. At, to, or toward the rear or back; backward.
2. In, to, or toward a former location: went back for the class reunion.
3. In, to, or toward a former condition.
4. In, to, or toward a past time.
5. In reserve or concealment.
6. In check or under restraint: Barriers held the crowd back.
7. In reply or return.

phrasal verbs

back away

To withdraw from a position; retreat.

back down

To withdraw from a position, opinion, or commitment.

back off

To retreat or draw away.

back out

To withdraw from something before completion.

To fail to keep a commitment or promise.

back up

To cause to accumulate or undergo accumulation: The accident backed the traffic up for blocks. Traffic backed up in the tunnel.

Computer Science To make a backup of (a program or file).

idioms

back and fill

Nautical To maneuver a vessel in a narrow channel by adjusting the sails so as to let the wind in and out of them in alteration. To vacillate in one's actions or decisions.

back to back

Consecutively and without interruption: presented three speeches back to back.

behind (one's) back

In one's absence or without one's knowledge.

have (one's) back up

To be angry or irritated.

off (someone's) back

No longer nagging or urging someone to do something.

on (someone's) back

Persistently nagging or urging someone to do something.

derivatives

bacḱless

adjective

back² (băk)

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[Dutch bak, from French bac, from Old French, boat, from Vulgar Latin* baccus, vessel, probably of Celtic origin.]

noun 

A shallow vat or tub used chiefly by brewers.