The speech you give when trying to civilly dump someone. It starts out saying a bunch of nice things about the dumpee, then has a negative turning point when the dumper says "but..." Most commonly used in season finales of The Bachelor and The Bachelorette as well as other dating reality TV shows.
Bachelorette: You're such an amazing person, and I've enjoyed getting to know you so much. But...I'm choosing the other guy.
Viewer: Oh man, she just gave him the but speech!