partner

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun One that is united or associated with another or others in an activity or a sphere of common interest, especially.
• noun A member of a business partnership.
• noun A spouse.
• noun A domestic partner.
• noun A lover.
• noun Either of two persons dancing together.
• noun One of a pair or team in a sport or game, such as tennis or bridge.
• noun Nautical A wooden framework used to strengthen a ship's deck at the point where a mast or other structure passes through it.
• intransitive verb To become partners or work or associate as partners.
• intransitive verb To be or make a partner of.

from The Century Dictionary.

• To join; associate as a partner.
• noun One who shares or takes part in anything; a sharer or partaker: as, to be a partner in one's joys and sorrows.
• noun One who is associated with another or others; an associate.
• noun One who is associated with another in some game or amusement: One who plays on the same side, as, specifically, in whist. One who dances with another, especially one of the opposite sex.
• noun One who is associated in marriage with another of the opposite sex; a husband or wife.
• noun One who is associated with another or others as a principal or the contributor of capital in a business or joint adventure, and usually shares its risks and profits. See partnership.
• noun pl. Naut., pieces of timber let in between two deck-beams, to form a framing for the support of anything which passes through a vessel's deck, as masts, capstan, or pumps.
• noun 1 and Friend, Companion, etc. See associate.
• noun In an involution, the element coupled with a given element.

from the GNU version of the Collaborative International Dictionary of English.

• transitive verb obsolete To associate, to join.
• noun One who has a part in anything with an other; a partaker; an associate; a sharer.
• noun A husband or a wife.
• noun Either one of a couple who dance together.
• noun One who shares as a member of a partnership in the management, or in the gains and losses, of a business.
• noun (Law) An associate in any business or occupation; a member of a partnership. See Partnership.
• noun (Naut.) A framework of heavy timber surrounding an opening in a deck, to strengthen it for the support of a mast, pump, capstan, or the like.
• noun See under Dormant, a.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun One of the pieces of wood comprising the framework which strengthens the deck of a wooden ship around the holes through which the mast and other fittings pass.
• noun Someone who is associated with another in a common activity or interest.
• verb to make or be a partner
• verb to work or perform as a partner

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a person who is a member of a partnership
• noun a person's partner in marriage
• noun an associate in an activity or endeavor or sphere of common interest
• verb act as a partner
• verb provide with a partner