1. To clog or obstruct something. Ugh, who jammed up the printer this time?

2. To quickly move or push something upwards. In this usage, a noun or pronoun can be used between "jam" and "up." Hey, be careful! If you jam those boxes up, you'll break something. I jammed the stick up a few times but couldn't get the ball out of the tree.

3. To cause something to clog or obstruct something else. In this usage, a noun or pronoun can be used between "jam" and "up." Ugh, what jammed the printer up this time? Oh, some crumpled pieces of paper.