permeant adjective 1noun 1forms 3 adjective1 •Able to pass through or into a given semipermeable membrane or polymer. noun1 •A substance which is able to pass through or into a membrane or polymer.The overall movement of permeants through a polymer is called permeation, which is a multistep process. — 2004 formspermeants · more permeant · most permeant