Given without an equivalent or recompense; conferred without valuable consideration; granted without pay, or without claim or merit; not required by justice.

costing nothing; "complimentary tickets"

lacking good reason; elements in a film, video or game which add nothing to the development of plot or character

unnecessary and unwarranted; "a strikers' tent camp...was burned with needless loss of life"

without cause; "a gratuitous insult"

Not called for by the circumstances; without reason, cause, or proof; adopted or asserted without any good ground; as, a gratuitous assumption.