When someone has played their guitar or bass guitar to the point that they are completely 'played out', or brain dead.
How you feel after playing an extra long set or gig.
"Man we've been jammin for six and a half hours. I'm guitarded."
Some dude at a bar when you just finished your last set and are rollin up for the night-"Hey I love you guys man you really sound great! Say, I play guitar too, and I was wondering if you wanted to jam.
You - "Sorry man, I'm guitarded. Not tonight."