To masturbate in a very specific way, involving both hands, one hand to choke one's self in a violent hateful way, the other hand to wrap around and under the leg to apply pressure and become numb. Then begin to masturbate vigorously while choking.
Person enioys domination and is no longer interested in good ol' fashioned salami slapping.
They begin to hatefuly choke themselves during the process out of frustration but it feels strange to do it alone .. what if someone else were involved? But they have no friends and nobody wants to touch their horrible body. How to make it feel as if someone else was stroking their johnson?
After experimentation they discover the reverse stranger and incorporate this, hooking their free arm around and under the leg to be sat and become numb before masturbating and choking, giving the feeling that a strange hand were performing the act.
Any house/apartment/frat house/trailer/etc. which is used for individuals to crash (sleep, chill, hang out, lurk, etc.) for a period of time. In order to "crash", one must not actually live there (e.g. have their name on the lease, own said flophouse, etc.). Flophouses are typically used by college students, drug addicts, transients, vagrants, or other unsavory characters.
A flophouse may also be the home owned by the parents of a college student, who after being away at college, wishes to live as if he/she is still at college (e.g. staying out all night, returning just to crash at mom and dad's house, then leaving again), rather than conforming to the pre-college rules.
Example #1
Dude: (Talking to someone passed out face first on the floor of his college apartment) Hey man, who the hell are you? What do you think this is, a flophouse??
Bro: Sorry dude, I must have passed out for a minute.
Example #2
Mom: Where have you BEEN for the last three days? You come home just to sleep?? What do you think this is, a flophouse??!!
A person you hate intensely not because they deserve such hatred but because they serve as a focus for your general hatred. A healthy way to dispense with excess animosity.