A binary operator representing logical disjunction (OR) in logic or the least upper bound in lattice theory.
Examples
Logical OR operation
p \vee q \text{ is true when either p or q (or both) are true}
Join operation in lattice theory
a \vee b = \sup\{a,b\}
Multiple disjunction in propositional logic
(p \vee q \vee r) \implies s