“All bets are off” is a slang expression of the English language. It is a comparative idiom used in a gambling context. In general, the phrase is used to indicate that a situation has become unpredictable. Individuals may also use the phrase as a way of expressing the end of a pre-existing agreement.
This phrase is an example of an idiom, and is one of many slang English sayings. In these types of expressions, the meaning of idioms is not meant to be taken literally. Rather, the words symbolically express a general idea or thought. This symbolism is typically achieved by comparing the intended meaning with a commonly understood concept. In this case, the meaning of "all bets are off" is being likened to a gambling situation.
In gambling, an individual plays a game by placing a bet — or wager — on a game's result. A bet is a financial or other personal stake that the individual is willing to sacrifice, and the individual places this stake on one of many choices. For example, in a roll of the dice an individual might predict that the dice will total the number 12 when rolled. If the individual is correct in his or her prediction, then a reward will be obtained in the form of gaining the amount of the bet back plus additional compensation. A wrong bet, however, will result in loss of the financial or personal stake.
This expression may indicate a change in circumstances that forces an altered viewpoint or action. If an individual is reasonably certain of the outcome of an action, then he or she can place a metaphorical “bet” on the outcome. If random chance or unpredictable factors call an action’s outcome into question, however, then a “bet” cannot be placed on the outcome with any degree of certainty. One may be certain that a picnic can be planned for a certain time, but if a sudden rainstorm occurs, then the planned picnic could be canceled or it may continue as scheduled. Therefore, “all bets are off.”
The “bets” in "all bets are off" may also involve some sort of agreement or understanding that has been reached. An individual may have agreed not to perform a certain action or get involved in a certain matter, for example. The “off” in the expression signals the possible termination of the agreement or understanding.
One should note, however, that the expression does not indicate an absolute reneging of the agreement or understanding. Rather, the individual is announcing that the possibility of a counteraction exists. In other words, the expression means that the alternative is being strongly considered.