A winter hat worn with the edges unfolded such that an excess of of the hat's material rises above the wearer's head, resembling the reservoir tip of a condom.
The term is often used as a shorthand identifier for the typical varieties of neon adorned "steezy" snowboarder bros who tend to be the primary exemplars of the fashion.
"Did you see that posse of reservoir tips that just climbed out of that Honda Civic?"
"Yeah, man... Looks like they are toking up before they go "shred the gnar" or whatever. Would you pass me my shades?... hurts like looking at the sun."
"Agreed. I'll go inform them it's not 1987 right away."