binary mekso operator: Let the inputs X1 and X2 be sets in the same universal set O; then the result of this operator applied to them is X1^c \cup X, where for any A \subseteq O, Ac = O \setminus A.
Generalizes to n-ary, for any integer n>1 or n being an infinity. This operator generates all three of the basic set operators: union (jo'e), intersection (ku'a), and relative complement (kei'i). See also: xa'ei'u. .krtis. calls it the "union(-type) hash operator", but has never seen a generally used name for it.