Definitions of bet:

• noun:   the act of gambling

  Example: "He did it on a bet"

• noun:   the money risked on a gamble
• verb:   maintain with or as if with a bet

  Example: "I bet she will be there!"

• verb:   stake on the outcome of an issue

  Example: "I bet $100 on that new horse"

• verb:   have faith or confidence in

  Example: "You can bet on that!"