gratūˈitous adjective

1. Without reason, ground or proof
2. Uncalled-for
3. Unnecessary or unjustified
4. Done or given for nothing
5. Voluntary
6. Benefiting one party only (law)

gratūˈitously adverb

gratūˈitousness noun

gratuitous promise noun (law)

A promise (not legally binding) made by one person to another when the latter has not provided any consideration in return (eg a promise of a gift)