2. a favorite girlfriend or boyfriend
3. a best friend, usually a dude, as in "my main man".
4. ebonics for "man"
5. main vein, the vein used to inject heroin, see also main lining
2. "that's my main girl"
Mains are chosen usually as their game play characteristics caters to the style of play of the gamer. Although some mains are chose out of media popularity of the character despite their inherit weaknesses (ex. Cloud Strife in Dissidia, Link in Soul Calibur, etc.).
Noobs often main characters which they can spam (repeatedly use the same move over and over with relative success in gameplay)
That noob mains Automatic because you can spam the a button and still manage 3000+ points.
"Aw, I've got the main munchies - lets go to the cafe bar and get some fat munch."
"HE was main goin' on about you all night. He totally want to get in by!"