v. Pretending to play a stringed instrument with a tune in the background; the obvious result being it will look as if the music were coming forth from the instrument itself.
Pickync is short for pick
synchronisation which is inspired by the more popular portmanteau
lip synchronisation (more commonly referred as lipsync.) Here, pick is taken to mean the little plastic/bone/ivory/metal whatchamacallit hoojamaflip
that certain guitar players (among several other stringed instrumentalists) use to strum their stringed instrument.
Depending on the degree of the observer's intelligence, thier attention to detail and their understanding of the concepts of vibrating length and thickness of the string, and the timbre of the instrument and its implications on the intonation and tone of the instrument, picksyncers may or may not pull off being real.
In all likeliness, picksyncers (good ones atleast) can only be made out as fakers by seasoned fellow operators of stringed instruments.
People always diss Lemolok on Youtube for picksyncing to a MIDI version of Necrophagist's Seven on a ukulele, but I think he did a fairly good job of making it look and sound real.