Class blast

When in an attempt to hold on a fart while in a classroom (preferably during reading, tests, or other times when the classroom is relatively silent) the pressure between the butt cheeks increases vibration- effectively making the noise louder. A shocked expression is a sign of a class blast, while pure embarrassment is a sign of just a regular fart.

Student #1: "Yo, this dude let out a class blast right as the room got quiet in 6th period today! His face was the best part.
Student #2: "I feel bad for him, all he wanted to to was hold it in, tie he fucked himsekf over. Still funny as shit though!"