1. fan, device which circulates the air; machine which helps a person breathe, respirator. ventilatorventi*la`tor , n. [cf. f. ventilateur, l. ventilator a winnower.] a contrivance for effecting ventilation; especially, a contrivance or machine for drawing off or expelling foul or stagnant air from any place or apartment, or for introducing that which is fresh and pure.ventilator n