Used to describe Trump supporters, especially the more extreme. Generally those that respond to "dog whistles" made by Trump to attack individuals or groups. Similar to the usage of brown-coats, but without relying on calling them literally Nazis.
Those redcaps just sent a bunch of death threats to another person's family...
He's been fine with going after anyone who doesn't agree with Trump since he became a redcap.
by LivingSerenity December 13, 2016
Traditionally, the most evil of all goblins whose cap is dyed red with the blood of his human victims. In recent times, this is a term to define the fugliest of all women. She will take domain in your home and not let you hang out with your friends.
Chris: "Hey Ryan, wanna go to the bar and watch the game?"

Ryan: "I can't man, Kara wants me to sit in my bedroom and hibernate all weekend."

Chris: "Damn dude, you gotta get rid of the redcap... so juicy."
by A Dub November 8, 2006
A member of the British Royal Military Police. Probably the world's most proffesional and well respected police force.
There was severe rioting in the city last night until they sent the Redcaps in.
by muffindamule October 6, 2006