Charter  is aircraft, motorcoach, or other mode of transportation reserved entirely for use by a group. 
 
Other definition:
Charter is to hire the  exclusive use of any aircraft, motorcoach, or other vehicle. 
Other definition:
Charter is a legal contract between an owner and an organisation for the  hire of a means of transport for a particular purpose. An individual traveller will use an intermediary to arrange to be carried on the  transport. Often applied to a flight which is the  result of a charter.
 
    
        
                                        