Full Idea
If P and Q are any two propositions, the proposition that either P or Q is called the 'disjunction' of P and Q, and is written P∨Q.
Gist of Idea
That proposition that either P or Q is their 'disjunction', written P∨Q
Source
E.J. Lemmon (Beginning Logic [1965], 1.3)
Book Reference
Lemmon,E.J.: 'Beginning Logic' [Nelson 1979], p.19
A Reaction
This is inclusive-or (meaning 'P, or Q, or both'), and not exlusive-or (Boolean XOR), which means 'P, or Q, but not both'. The ∨ sign is sometimes called 'vel' (Latin).