look up any word, like fleek:
 
1.
when two boys' mothers are sisters and share the same father
my brother is also my cousin by blood becuase we share the same father and our mothers are sisters, brother+cousin= brousin
by CO-DAY! July 01, 2009
 
2.
The above definitions are correct, but I'll also add that brousinhood can occur without some weird babymaking with two women who are also siblings. Another instance of brousinhood is when a family adopts their niece or nephew, later having kids of their own, making the adopted child and the newborn baby both brothers and cousins.
Stranger: Eminem, are your kids sisters or cousins?

Eminem: Well I adopted one from my ex-wife's sister, so I guess that makes them brousins...
by explicittt39 August 18, 2011
 
3.
WHEN YOUR FATHER MARRIES YOUR AUNT WHO ALSO HAS A SON.
HE USED TO BE MY COUSIN... BUT NOW HE'S MY BROUSIN.
by bored rrt's February 19, 2011
 
4.
a misspelling of "browsing", as in just posted, doin ya thang, browsing through the women you see... lookin for a night, not a lifetime
"we be runnin' through these women by the thousands, ain't no relationships, just hittin it and quit and we be 'brousin'"

"and best believe when I come see you, I'z gon 'brous' on the way"

- from 11/5's classic track "Brousin'"
by d0sia July 19, 2009
 
5.
A cousin who is more like a brotha
"Is that your brother?"
"No, we're cousins, well actually we're brousins"
by HersheySquirts August 09, 2005
 
6.
A cousin by blood, but a brotha in life. Your boy. Your life-long best friend.
"Damn kid, your cousin is a balla."
"Yeah he is! ... And he's my brousin. I known that kid my whole life -- he's like a little brother."
by Hersheysquirts Sr. September 21, 2005