The unknown and unpredictable element in happenings that seems to have no assignable cause. A force assumed to cause events that cannot be foreseen or controlled; luck: Chance will determine the outcome. The likelihood of something happening; possibility or probability. Often used in the plural: Chances are good that you will win. Is there any chance of rain? An accidental or unpredictable event. A favorable set of circumstances; an opportunity: a chance to escape. A risk or hazard; a gamble: took a chance that the ice would hold me. Games A raffle or lottery ticket. Baseball An opportunity to make a putout or an assist that counts as an error if unsuccessful. Caused by or ascribable to chance; unexpected, random, or casual: a chance encounter; a chance result. To come about by chance; occur: It chanced that the train was late that day. To take the risk or hazard of: not willing to chance it. on To find or meet accidentally; happen upon: While in Paris we chanced on two old friends. by chance Without plan; accidentally: They met by chance on a plane. by chance Possibly; perchance: Is he, by chance, her brother? on the off chance In the slight hope or possibility.