1] the male equivalent of PMS
2] a state of irritability, moodiness, and occasional bloating that occurs only in men
"Man, what's up with Brad? He's wearing sweatpants and glaring at everyone."
"Oh yea he's just He-MSing, he couldn't zip up his jeans and has been cranky all week."
The male version of PMS. When a male is being really bitchy and/or having mood swings.
Carl: Hey Steve, how was your day today
Steve: Fucking bullshit, my boss made me fax 20 sheets and i spilled coffee on my new Italian shoes. Also, my co-workers are so damn chirpy and so annoying and the computer was being a bitch and i'm sick of all this Recession shit and (continues bitching and moaning)
Carl: You got a real case of He-MS going, don't you?
Steve: Fuck you