First said by Ryan Lawrence known for being a terrible fantasy baseball manager who values talents such as John Buck and Yovani Gallardo who are both terrible players. The word has no real meaning and is used whenever you want

/ˈhæpən/ Show Spelled Pronunciation hap-uhn
–verb (used without object)

to ejaculate; to cum;jizz.

It's a more socially acceptable version of "shit happens".
It can be used to:
1)express condolences for someone's situation without offering any apologetic words.
2)respond to a future problems that shows a sense of sadness/aggression towards it, but in a way without trying to complain
3)to shrug off a one's own, or someone else's, minor annoyance
4)substitute for an actual response, while still continuing the conversation

Phrase said after something strange or weird has occurred in your presence

1. an event, band, person or anything that is not cool, interesting, or attractive. usually used to give a negative recommendation about something

a phrase said after u do something stupid or something happens to you. usually used by one of your friends made popular by tom marchin

The worst film ever made, written directed by lame arse director M. Night Shaylaman. The idea isn't that bad but the ending explained nothing and looked as if it had been finished in 10 minutes in the pub on the last day of filming.