As a Noun:
1. A situation in which it is possible for something to happen, especially a situation which is unexpected and beneficial. English = opportunity, chance.
2. The arrival of someone somewhere, especially unexpectedly. English = appearance.
As a Verb or Adjective:
1. To take place without planning and unexpectedly. English = pop up, appear.
2. To be present unexpectedly at a place. English = pop up, appear.