gratuitous
hackneyed
incessant
insidious

1._______________(adjective) going on without stopping or in a way that seems endless
2._______________(adjective) used so often that it has become stale or dull
3._______________(adjective) given or gotten free
4._______________(adjective) dishonest, sly or tricky

Answers

1. incessant
2. hackneyed
3. gratuitous
4. insidious