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2.
A cousin who has the characteristics of a "bro"
My mother's nephew is such a brosin
by Blade Smith December 28, 2009
 
1.
A half-brother who is also your cousin. The male offspring resulting when your sperm donor also impregnated your mom's sister. The male version of a couster.
I used to get along really well with my cousin Jake, until I found out we had the same dad. Now he's my brosin, and it's kinda awkward.
by Bructus August 16, 2010
 
3.
Shopping/browsing with your bros but no homo.
Scott: Dude thats a sick sweatshirt. Is that new?
Taylor: Yeah, I got it this weekend when me and Luke were brosin' at the mall.
by thowe January 05, 2010
 
4.
A friend or family member who maintains the highest standards by hooking up and having children with two members of the same family.
Jane Doe hooked up with John Doe, had a son..then hooked up with John Doe's brother and had another son..therefore the kids are not only brothers they are also cousins.

Brothers+Cousins = Brosins
Brosins - pronounced Brah-sins
by RUkiddin'me August 03, 2011