Autoharp 

An instrument similar to a harp, in the sense that it has dozens of strings, but is rather small in size and has buttons that change the sounds so you can play different chords all across the strings by strumming. When you press a chord button, it presses down a long rod with pieces of felt attached. The pieces of felt press down on strings of which are not used for the particular chord and leaves certain strings free to sound for that particular chord.

That man plays the Autoharp while he sings.

Autoharp by RabbiMordcha January 5, 2015

Rusty Autoharp 

The act of performing anilingus on one's girlfriend and simultaneously reaching around to stimulate her vaginal area by hand. Term derived from the "rusty trombone" as women are not equipped with a trombone-like appendage; moreover the originator of the term maintains that while they do not know how to play the autoharp, the term merely sounds hilarious.

Kenny was going down on me last night, then went to the back door and gave me a rusty autoharp!

Rusty Autoharp by dirty-ass mofo November 6, 2010

autoharpomania 

An often progressively debilitating psychological disorder falling on the obsessive compulsive spectrum, usually beginning in childhood, whereas the sufferer becomes fixated on the autoharp, an oddly non-musical zither instrument, to the exclusion of everything else.

When the once gregarious and popular young man stopped eating or speaking to anyone and we suspected he may be suffering with autoharpomania, we made the decision to intervene and were horrified to discover no less than one hundred and fifty autoharps amassed in young Phinneas’ bedroom.

autoharpomania by Dr Bunnygirl June 16, 2021