Noun- Abbreviation for Junior Varsity, often used to point out something/someone not up to a high level or demonstrates inexperience.
Verb- To refuse to participate in a fun activity, typically to do homework or to go home and pretend to do homework while actually going on facebook. More generally, to bitch out. This is also used in its unabbreviated form, "to Jon Victor."
You didn't log off of facebook and someone changed your status? That's a JV mistake.
That party was pretty JV- it was lame and everyone passed out at 11:00
That guy just JV'ed out of the White Panda Concert to go study.
We were going to go to Chick-fil-a with Jon but he JV'd and went home to go on facebook instead.