In Back to the Future Marty is rocking Johnny B Goode on his guitar, starts a solo, and then it turns into some kind of guitar molestation. I’ve been told Jimmy Hendrix was known for doing this too. Is there some official musical terminology for this?
“wanking”
Grape?
Could guitar ever consent?
And I’ve never heard of sticky guitar.
No but it will gently weep afterwards…
Well, if it smokes afterward, it was probably good for the guitar.
Are you thinking of shredding, maybe?
Fretboard masturbation?
Skronk.
Frettage.
+1
Also known as " Musical Wankery"
I like it!
I’ve heard “fret wank” which covers a couple of suggestions made already.
- another vote.
Also known as “when the lead guitarist detaches from the rest of the band and disappears up his own asshole.” **Jack Black *offers up another memorable example of this when he stage dives at the start of School of Rock, too - and comes across as just as big of a tool.
*count me as one of those folks who normally enjoys Michael J. Fox and '80’s-type movies, but finds the thought of the scene where “Chuck Berry’s cousin” tips Chuck onto Marty’s guitar moves as over-the-line offensive…on a few levels.
Yup, wanking, or possibly noodling.
The question is, did Michael learn from Pete, or did Pete copy Marty? 
Michael J. Fox plays and is into gear; he bought a few of Clapton’s guitars at the first or second Crossroads Auction. I have no idea about the status of his playing since his Parkinson’s or if he was any good as a player before the onset…
Are you talking about what he’s doing around 2:16, where he’s lying on the stage and pushing himself along with his feet? I can see how that might be characterized as “humping the guitar,” but I really think he’s just lifting his hips so he can push himself along sliding on his shoulders.
F-holes or jack?
Can you do it with a keytar?