A fourway is when two couples share their partners with each other. A bit like a foursome but not all participating in the 'activities' at the same time.
Hey dude, did you hear about Cindy and Bob having a fourway with Betty and Ken?
by 123Anonymous12333 March 14, 2010
The hazard warning lights on a car. When this button is pressed, all the indicators (orange in Europe) flash simultaneously.
"His car broke down so he put his four ways on"
by man98763 February 05, 2006