This happens when when you hook up with a girl at her house or apartment. After sexy time, you take dump in one of her slippers. The next morning when she puts on her slippers, you yell, "DIRTY SLIPPER!" and smack her in the face, then run out of the house screaming and laughing.
by steve-n-craig January 18, 2014
Grandpa's Dirty House Slipper, in keeping with the definition of House Slipper, is the act of an elderly male homeowner engaging in unprotected anal sex with a male residential services provider, i.e., home health aid, lawn care worker, maid, plumber, cable guy, in exchange for the worker to provide free or extra services.
Howard needed his lawn mowed and the shrubs trimmed around his yard. However, his social security check only stretched so far and he could not afford to pay for those services. Therefore, Howard availed himself to sex and performed a Grandpa's Dirty House Slipper with a young male lawn care worker mowing the yard of his neighbor's home. Howard ended up with neatest yard and the best groomed shrubs in the whole community.
by Eaton Holgoode April 26, 2014