look up any word, like cleveland steamer:
 
8.
Combination of Brother and Sister
A brother who acts girly, or sister who's one of the lads !
Could be used for friends, with platonic friendship.

Broster : '' Like a sibling, but even better.''
by Rednosedee October 20, 2009
 
9.
1) Short form word describing one's sister-in-law's brother, as it is ordinarily too long and complicated to explain the relation - as the individual is not really family, but is more than a random friend
1) I'm heading out on the town tonight with my broster
by Heeeres Johnny April 08, 2011
 
10.
The term commonly used for your sister who looks like she could be your brother.
Hey bitch, I didn't sleep with your broster!
by Dale April 19, 2005
 
11.
IN some parts of South-East England, the word 'Broster' is used to describe something that has gone seriously wrong. The term was derived from one AS chemistry student who relentlessly dropped glassware by accident throughout the year. As the term became more widely used, to 'Broster something up' or 'brostered' became used for anything that has gone badly wrong, so it was no longer only applicable to broken glassware.
Boy 1 (Drops glass test tube)
Boy 2 - Dayemm fool, you brostered that up big time
by Benenenenenenenenenenenen December 06, 2010