A) A quality that makes people in possession of it the epitome of cool. When trying to explain why this person is so cool you come up blank. Everyone knows this person and people like being around them.
B) Used to describe someone whos not necessarily hot but you are strangely attracted to.
"Hey do you know Jim?"
"Oh yeah, who doesn't. You know what's weird?"
"Despite his shortness and slight chubbiness, I kinda want him..."
"That's cause he's got X factor..duh."