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1.
extreme pimpin, seven gurls or more
dating 7 gurls at once, and not having any of them know = gillin
by saia January 19, 2006
 
2.
Coming from the verb 'to Gil'; talking closely in someone's personal space in a most annoying manner, causing severe discomfort.
Sean: "Why you steppin' up? There's no need for gillin'"

Sam: Cut it out, you're gillin' me!
by Sam McGee August 12, 2006
 
3.
When a guy is in such a grumpy, pissed-off state, it's like he has male PMS.

A very irratible dude. Is known to become easily pissed off, brash, rude and sarcastic.
Dude, I was at TMobile the other day, and the guy helping me was totally gillin. I asked him to show me how to change the apps on my phone and he totally bit my head off!
by RonnieDelS June 22, 2010