To make ware or aware; to give previous information to; to give notice to; to notify; to admonish; hence, to notify or summon by authority; as, to warn a town meeting; to warn a tenant to quit a house.
To give notice to, of approaching or probable danger or evil; to caution against anything that may prove injurious.
notify of danger, potential harm, or risk; "The director warned him that he might be fired"; "The doctor warned me about the dangers of smoking"