given, done, bestowed, or obtained without charge or payment; free; voluntary.
2.
being without apparent reason, cause, or justification: a gratuitous insult.
3.
Law. given without receiving any return value.
Origin: 1650–60; < Latin grātuītus free, freely given, spontaneous, derivative of grātus thankful, received with thanks (for formation compare fortuitous); see -ous
1656, "freely bestowed," from L. gratuitus "free, spontaneous, voluntary," from gratia "favor." Sense of "uncalled for, done without good reason" is first recorded 1691.