Shitblocker

(noun) A person, thing, or event that prevents you from taking a much needed shit, and may or may not consequently cause you to shit in your pants. May also be used as a verb (shitblock). The person could be a cop who pulls you over for speeding - you were speeding because you had to shit so bad. It could also be an annoying guy or girl at a party who stops you to make a bad joke, or, for those in grade school or highschool, the teacher who will not let you use the restroom.

Dan was being quite the shitblocker today - I told him I had to use a restroom and that it was an emergency, but he just wouldn't let me go.

Man you got shitblocked today when that cop pulled you over for speeding.