WordWeb Online

1. (of an event) come to pass (in time, so that it is real and actual at some time)
   "What is happening?";
   - hap, go on, pass off, occur, pass, fall out, come about, take place
    
2. Occur or be the case in the course of events or by chance
   "It happens that today is my birthday";
   - befall, bechance [archaic]
    
3. Chance to be or do something, without intention or causation
   "I happen to have just what you need!"
    
4. Come into being; become reality
   "Her dream really happened";
   - materialize, materialise [Brit]
    
5. Come upon, as if by accident; meet with
   "I happened upon the most wonderful bakery not very far from here";
   - find, chance, bump, encounter

Derived forms: happened, happening, happens