pso·ra·len \ˈsōrələ̇n, ˈsȯr-\noun (-s) Etymology: modification of New Latin Psoralea psoralea : a substance C11H6O3 found in some plants that photosensitizes mammalian skin and is used in conjunction with ultraviolet light to treat psoriasis ; also : any of various derivatives of psoralen having similar properties