adj 1  :  compounded or consisting of or marked by two things or parts  2 a  :  composed of two chemical elements, an element and a radical that acts as an element, or two such radicals  b  :  utilizing two harmless ingredients that upon combining form a lethal substance (as a gas) .
 
   
 
Published under license with Merriam-Webster, Incorporated.  © 1997-2024.