You've drawn something. It's finished, but then you take a second look at it and there's just something missing about the drawing. You try your best to figure out what it is, but then you just end up wondering in front of the picture looking at it for more than three hours.
You come to a realization. You have officially hit a block.
In the end, you just settle with whatever you just came up with and when people ask you if that's all the drawing is, you say "Yea, I'm going for that you know, more pop-art look type of drawing".