n, pl  bas*es   1  :  that portion of a bodily organ or part by which it is attached to another more central structure of the organism <the of the thumb>   2 a  :  the usu. inactive ingredient of a preparation serving as the vehicle for the active medicinal preparation <the fatty of an ointment>   b  :  the chief active ingredient of a preparation - called also basis   3 a  :  any of various typically water-soluble and bitter tasting compounds that in solution have a pH greater than 7, are capable of reacting with an acid to form a salt, and are molecules or ions able to take up a proton from an acid or are substances able to give up an unshared pair of electrons to an acid - compare ALKALI   b  :  any of the five purine or pyrimidine bases of DNA and RNA that include cytosine, guanine, adenine, thymine, and uracil based adj 
 
 
 
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