Disjunction

Disjunction[expr, {a1, a2, ...}] gives the disjunction of expr over all choices of the Boolean variables ai.

Examples

Disjunction over Boolean variables:

Disjunction[a && b, {a, b}]
(* a || b *)

Expand logical expression:

Disjunction[a || b, {a}]
(* True *)

Please visit the official Wolfram Language Reference for more details.