2. The act of getting ready to go somewhere, especially the act of getting ready to drive somewhere
3. The act of a woman climbing on top of a man to ride him
2. Aren't you ready to leave yet? Saddle-up, you slow be-yotch.
3.Ralph: Oh baby, I want you so bad!
Jenny: Sit back and relax hon, I'm about to saddle up.
Popularized by American "Old Western" films, where horses were the primary means of transportation. When someone saddled up their horse, it was often because they were about to leave.