Funkjam is a style in which a lead guitarist, a bassist and a drummer can jam together. It is in the style of funk, which means the notes are syncopated. Usually both the bass and lead guitar use pentatonic scales.
There are different styles of funkjam:
The guitarist plays with very low gain and reverb on the bridge pickup and a wah-wah pedal. The bassist plays clean with smooth, finger picked notes and can include some light slapping. The drums are light.
The guitarist plays with medium/high gain in either the bridge pickup of the neck/middle pickup. The bass plays with low gain and heavy slapping. The drums are very heavy with lots of cymbal crashes, in other words, the drummer has a spaz-out.
Red Hot Chili Peppers normally play a funkjam for the intro of their gigs.