The act of shitting into a sink, then "flushing" by running the garbage disposal. Performed as a last resort, only when all other toilets are in use. Frequently involves beer shits the morning after.
"Mike had to drop a log in the chipper because his girlfriend and her roommate were using the bathrooms."
Derived from the word transmission, when a car's transmission breaks down, but is not limited to that. If a car has a flat tire, or is not drivable, then it dropped a tranny.
Jim: Are you coming over to my house tonight?
Mike: Yeah, as long as my car doesn't drop a tranny.