psi·lo·sis \sīˈlōsə̇s\noun (pluralpsilo·ses \-ōˌsēz\) Etymology: New Latin, from Greek psilōsis, from psiloun to strip bare, leave naked, pronounce without aspiration, (from psilos bare) + -sis 1. a.: a falling out of hair b.: sprue 2.: failure to pronounce aspirate sounds