Gratuitous (adjective)

1. Given or done without payment or recompense.
2. Given or done without good reason or justification.

Origin:

From the latin word "gratuitus" meaning "free, given freely".

Examples:

1. The gratuitous violence in the movie was unnecessary and disturbing.
2. It was a gratuitous insult, completely uncalled for.
3. He gave her a gratuitous compliment, one that she knew was insincere.
4. The company offered a gratuitous service, one that was not requested or paid for.
5. The gratuitous use of profanity in the novel made it hard to take seriously.