A euphemism for taking a long shower purely for masturbation. One may take one despite already having a shower to clean. The shower nozzle may or may not be used.
Man, I just had the best 40 minute shower!
. Mind if I have a 40 minute shower? Feel free to go home if you don't want to wait around for that long...
Mary loved to take 40 minute showers when her boyfriend went away on business trips.