To have a large ego about ones vagina. Similar to having a "Big head" and thinking your better than everyone else, but in this case thinking your vagina is better than everyone else's. Like you have the tightest sexiest Coochie in town. Your twat is hott and you know it.
"Did you see brooke working it on the dance floor? She must have a serious case of GinerSwell."
"Damn dude Anai-i looked straight up GinerSwell in those booty shorts."