Used to indicate to a partner that proper precautions have been taken and there will be little to no chance of a "mess" during anal sex. It is also free of any graphic words that might spoil the mood. Unlike. "my rectum is free of feces"
Having spent 20 min in the shower Chad emerged and proclaimed to his boyfriend "Alright I'm bottom ready lets fuck"
Frank asked his Girlfriend if she was bottom ready before they were to have anal sex. She looked confused and shrugged. Frank stuck it in her snizz instead.