: one that is under the protection of another : dependent a first-rate power, able to defend her political clients in central and eastern Europe —W. W. Kulski 2 a : a person who engages the professional advice or services of another a lawyer's clients a personal trainer … enjoyed the challenges of helping clients buff up their bodies. —S. K. Parks b : customer hotel clients a restaurant's clients c : a person served by or utilizing the services of a social agency a welfare client d : a computer in a network that uses the services (such as access to files or shared peripherals) provided by a server also : software that allows a computer to function as a client in a network