A male that is the master of making things floppy (loose) during intercourse.
Tom: "Who dated Susan last?"
Jim: "Larry did why?"
Tom: "She was so loose last night. Larry must be the flopmaster!"
When a person makes plans and doesn't show up or does not follow through with the plans, they flop. This person becomes a flopmaster after not following through on a consistent level.
Alex: Hey man! I'm coming to visit you in three weeks!
Brandon: Okay, sweet!
*3 weeks later*
Alex: Yaaaaa. My mom said I have to work.