Having plans cancelled at the last minute. Usually occurs when the person with whom you had plans gets a better offer, or is too tired/hungover/grouchy/pissed off at you to want to hook up.
I was going to have dinner with my homie, but he was too sleepy to go so he rainchecked me.
The most awful teacher of Bermudian History, Terrible teacher who expects the students to treat her class like it’s the only responsibility and gives us work based on that notion, Old Hag who owns a Pig Farm and is secretly Anne Frank