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1.
(adv/adj) Denoting work undertaken by a bro for the good of one's bro without compensation, esp. when that bro needs help moving, a ride to the airport, or even a temporary wingman. Such work is considered just as noble, or perhaps nobler, than other voluntary service.
(adv) I do kinda have something else broing on tonight, but after I rackjacked Ted last night, I feel like I have to throw him a brone and help him hook up with Robin pro brono.

(adj) Might I enlist your pro brono services, gentlemen? This Tijuana prostitute isn't going to bury itself!
by Dinkmers August 20, 2009
 
2.
When a bro or some bros get together to volunteer for a good cause.
bro1: "Jesse is going down to help with the beach clean up crew today."
bro2: "He's all about that pro brono"
by sebastian crucial February 02, 2007
 
3.
Doing something nice for a friend just cause he's your bro
"I heard Doug got you home last night cause you were trashed."

"Yeah, he didn't want to leave, he just did it Pro Brono"
by Great Brown Hope October 17, 2011
 
4.
a homosexual charity fuck
He looks like Balki Bartokomous so i'll consider this PRO BRO-NO.
by hough August 11, 2008