When someone who plays the drums goes through a phase of not being able to play the particular instrument well, or not being able to write music.
Lack of Creativity
Lack of Motivation
similar to Writer's Block
"comon, lets play.. 1... 2... 3... 4...
Dude, I can't I have Drummers Block"
"I would go on the drums.. but I cant be bothered..
Hey - you've got Drummers Block"