(in the theory of classes) the class that includes all other classes and is composed of all individuals composing these classes.
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British Dictionary definitions for universal class
(in Boolean algebra) the class containing all points and including all other classes
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012