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.
When you go home with a fugly chick and begin to sober up you realize you can't sleep with this girl. When she goes to the restroom to prepare herself for sex, you pull the sheets and covers down, dump all over the bed and pull the sheets back to cover your crap. Then run like hell!
Two gentleman meet in the sleeper cab of Peterbilt at a rest stop off of I-194, one man (the giver) places a tight band around the other man's (the receiver's) genitals, massages his crotch the point of release, but the band prevents the receiver from ejaculating until after the giver has also finished, thus resulting in a "Bismarck Raincheck".
I was on a cross country trip to my father's funeral when I stopped to give some lonely trucker a Bismarck Raincheck