To keep safe; to defend; to guard; to prevent harm coming to.
To book a passenger on a later flight if there is a chance they will not be able to board their earlier reserved flight.
To caution or admonish (someone) against unwise or unacceptable behaviour.
To notify or inform (someone, about something).
To give warning.
To summon (someone) to or inform of a formal meeting or duty.
To advise or order to go or stay away.
To make (someone) aware of impending danger, evil, etc.