From WordNet (r) 2.0 (August 2003) [wn]:
happening
adj : taking place; "the parade is still happening"
n : an event that happens [syn: occurrence, natural event]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
happening \happening\ n.
1. something that happens; an occurrence; an event.
Syn: occurrence, natural event.
[WordNet 1.5]
2. Specifically: An event that is particularly interesting,
noteworthy, or important.
[PJC]
3. An artistic or entertainment event that is unconventional,
sometimes discontinuous, designed to evoke strong
emotions, and sometimes involving participation by the
audience.
[PJC]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Happen \Hap"pen\ (h[a^]p"p'n), v. i. [imp. & p. p. Happened
(-p'nd); p. pr. & vb. n. Happening.] [OE. happenen, hapnen.
See Hap to happen.]
1. To come by chance; to come without previous expectation;
to fall out.
[1913 Webster]
There shall no evil happen to the just. --Prov. xii.
21.
[1913 Webster]
2. To take place; to occur.
[1913 Webster]
All these things which had happened. --Luke xxiv.
14.
[1913 Webster]
To happen on, to meet with; to fall or light upon. "I have
happened on some other accounts." --Graunt.
To happen in, to make a casual call. [Colloq.]
[1913 Webster]