man furnace 

The testicles, vas deferens or any part of the male genitalia that produces semen.

Would you like some hot jizzum from my man furnace?

man furnace by nion0 January 6, 2008

Furnace man 

A 4th class or otherwise entry level power engineer/stationary engineer or boiler fireman, especially ones that do janitorial/housekeeping duties such as mopping floors as well as boiler maintenance, this term is largely considered outdated.

Mommy I don’t want to go to school! The furnace man is always hiding in the Girls bathroom!

Furnace man by Hell’s Bells 1980 April 2, 2023