Or of an expression over all True/False assignments of the given variables (minimized)
Disjunction[expr, {a1, a2, …}]
Disjunction[Nor[a, b], {b}]
→ !aDisjunction[f[a, b], {a, b}]
→ f[True, True] || f[True, False] || f[False, True] || f[False, False]Disjunction[f[i, j], {i, j}]
→ f[True, True] || f[True, False] || f[False, True] || f[False, False]