(noun)
(informal) broadly, something that is offered free of charge (complimentary), often as compensation for something, especially a voucher, pass, or ticket for something;
e.g. I received a comp to attend the concert as a favor from the band. The resort offers many comps to its guests.
(noun)
(informal) a compilation or a composition of media, especially of music, or the music that is played to accompany something;
e.g. She is busy working on the comp that she plans to play at the recital.
(verb)
(informal American) to provide something for free, usually as compensation or a promotion, or to give someone something at no charge;
e.g. The restaurant agreed to comp his meal because of the bug he found in his food. They will comp her for the services because they did not deliver what they promised.
(verb)
to provide accompanying music, especially to a jazz solo by playing chords;
e.g. He learned how to comp by playing with other musicians.
(adjective)
free or complimentary, available at no charge;
e.g. They won comp passes to the performance by entering a drawing.