backer

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

• noun One that backs a person, group, or enterprise.
• noun One who bets on a contestant.
• noun One who provides or works with backs or backing.

from The Century Dictionary.

• noun One who backs or gets on the back: as, a backer of untamed horses.
• noun One who backs or supports, or who aids and abets, another in an undertaking, especially in any trial of skill, agility, or strength; also, one who bets or “lays” his money in favor of a particular person, horse, etc., in a contest; one who indorses the notes or sustains the credit of another.
• noun In architecture, a narrow slate laid on the back of a broad square-headed one, where the slates begin to diminish in width.
• noun Nautical, a strap of rope or sennit fastened to a yard-arm to secure the head-earings of a sail.
• Same as backermore.

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

• noun One who, or that which, backs; especially one who backs a person or thing in a contest.

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

• noun One who, or that which, backs; especially one who backs a person or thing in a contest.
• adjective phonetics comparative form of back: more back

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

• noun invests in a theatrical production