penetrant

from The Collaborative International Dictionary of English v.0.48

Penetrant \Pen"e*trant\, a. [L. penetrans, p. pr. of penetrare:
   cf. F. p['e]n['e]trant.]
   Having power to enter or pierce; penetrating; sharp; subtile;
   as, penetrant cold. "Penetrant and powerful arguments."
   --Boyle.
   [1913 Webster]