tenuis
noun
ten·u·is ˈten-yə-wəs 
plural tenues ˈten-yə-ˌwēz
-ˌwās
: an unaspirated voiceless stop
Word History
Etymology
borrowed from Medieval Latin (as translation of Greek psīlós "bare, plain," applied to the consonants π, τ, κ), going back to Latin, "thin, narrow, slight" — more at thin entry 1
First Known Use
1650, in the meaning defined above