1. when you and your friends hang out, [rock out], etc.
2. when a person, preferably a [hard-core rocker], gets onstage and totally kicks butt at playing the guitar or drums.
3. when a person makes a peanut butter and jelly sandwhich and loads all of the jelly in the jar onto his/her sandwhich, and bites into the sandwhich, an the jam falls on his lap and they don't know it.

> * man, we are totally jammin' out!!! let's rock!!
> *man, you totally jammed out onstage tonight! let's go get drunk and reminisce!
> *man, i totally spilled all of the jelly on my lap! now i can say im totallyjammin out!