Entry 1 sense Webster, 1913 Rancidity /(răn*sĭd"ĭ*ty̆)/ · Ran·cid·i·ty · IPA /rænsˈɪdɪtiː/ 01 n. The quality or state of being rancid; a rancid scent or flavor, as of old oil. 1. The quality or state of being rancid; a rancid scent or flavor, as of old oil.