Definitions of warn:

• verb:   notify, usually in advance

  Example: "I warned you that I would ask some difficult questions"

• verb:   ask to go away

  Example: "The old man warned the children off his property"

• verb:   notify of danger, potential harm, or risk

  Example: "The director warned him that he might be fired"

• verb:   admonish or counsel in terms of someone's behavior

  Example: "I warned him not to go too far"

• name:  A surname (very rare: popularity rank in the U.S.: #25913)