Tremense is a cross between a tremendous and an immense event. Tremense is the word used when no other word can describe the epic proportions of what just happened.
The series of rank farts leading up to a huge shit, much like the tremors leading up to the eruption of a volcano.
Guy1: Dude, that smells horrible. What did you eat, this has been going on for a few hours.
Guy2: I feel like I'm going to erupt
Guy1: Oh, you must have shit tremors