What is the meaning of Nighthawk?

A nightjar, especially Caprimulgus europaeus (Eurasian nightjar).

A New World nightjar of the genus Chordeiles, especially Chordeiles minor.

A person whose preference or custom is to remain awake and active during the night and the early morning hours.

A nighthawker (metal detectorist who works illegally at night).

Source: wiktionary.org