the act of showering with more than one person for the benefit of using less water.
Me and this lady took an Eco Shower. I totally saved the environment!
A shower consisting of two or more people. It is usually a device that's used to legitimize having sex in the shower. Saving water has never been so fun.
Guy: That's so cool that you spend a summer in Japan saving dolphins. You know I'd be willing to take an Eco Shower with you if you'd want to save the environment a little more.
Girl: Ok! Anything to save the Earth!