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1.
Lycra tight fitting surf shirt that protects surfer's stomachs, backs and upper body from rash that comes from rubbing up against surfboards.
"Dude i'm so glad i wore my rashguard! Did you see that crazy ass Kevin's bleeding raw stomach?! He should have worn a rashguard."
by Luckila Margarita June 08, 2005
 
2.
A thin shirt made out of a stretchy material worn by surfers. It is worn on the upper body to protect from reef rash.
Brian wore a Rash Guard after that big hit he took last month and tore up his back.
by Andrea May 06, 2005