Merriam-Webster Collegiate Dictionary - bet

 I. noun  Etymology: origin unknown  Date: 1592  1.  a. something that is laid, staked, or pledged typically ~ween two parties on the outcome of a contest or a contingent issue ; wager — often used figuratively in such phrases as all ~s are off to stress the uncertainty of an outcome  b. the act of giving such a pledge  2. something to wager on  3. a choice made by consideration of probabilities your best ~ is the back road  II. verb  (~; also ~ted; ~ting)  Date: 1597  transitive verb  1.  a. to stake on the outcome of an issue or the performance of a contestant  b. to be able to be sure that — usually used in the expression you ~ you ~ I'll be there  2.  a. to maintain with or as if with a ~  b. to make a ~ with  c. to make a ~ on  intransitive verb to lay a ~  III. abbreviation ~ween