When someone in a position above you at work gives you an assignment to do that is technically their job, but it's such a crappy task they don't want to do it so it's passed on to you.
"I have to work late, my boss crap dumped a bunch of paperwork on me."
"I'd like my job more if everyone would stop crap dumping on me."
To make a bad situation or anything that is in shitty condition worse.
Come on man, don't smoke weed after I just got a ticket!
You're crapping/taking a dump on a pile of shit!