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.

Shitblock

What your roommate does every morning, when they occupy the restroom for an eternity and you really need to take a dump. They also may or may not leave some of the most heinous smell there after they're finally done, making you question whether you really need to go that bad.

Person: *bangs on bathroom door
Roommate: "Just 40 more minutes!"
Person: "You've been there for two hours already, stop shitblocking me!"