Noun

1. A possibility due to a favorable combination of circumstances
2. An unknown and unpredictable phenomenon that causes an event to result one way rather than another
3. A risk involving danger
4. A measure of how likely it is that some event will occur; a number expressing the ratio of favorable cases to the whole number of cases possible
5. The possibility of future success

Verb

1. Be the case by chance
2. Take a risk in the hope of a favorable outcome
3. Come upon, as if by accident; meet with