moonlighting

To work on the side (at a secondary job), often in the evening or during the night.

(by extension) To engage in an activity other than what one is known for.

(by extension, of an inanimate object) To perform a secondary function substantially different from its supposed primary function, as in protein moonlighting.

To carry out undeclared work.

A period of working on the side (at a secondary job), often in the evening or during the night.