When a Bro commits an act that is considered bogus to another Bro.
Bro #1 - "Hey, Bro. Don't be mad, but I hooked up with your ex last night at a party."
Bro #2 - "Bro, why you do me Brogus?"
Bro #1 - "Sorry Bro, I didn't mean to do you Brogus. She was just coming on to me, and I thought that it was cool since you guys broke up like, a year ago."
Bro #2 - "We broke up last week, Bro. That was so Brogus."
A mixture of being sullen, morose, removed, unmotivated, distracted, unusually quiet, etc.
Being broygus can be tied to being depressed, though broygusness is generally a temporary condition.
Generally those considered "broygus" are a buzzkill.
Todd, "Yo peeps who's excited for tonight?"
Bryce, "Well we all would be if Jamie wasn't completely broygus."
Jamison, "I am definitely pretty broygus."
Nuñez, "Yeah dude and it's seriously bringing us all down."