Definition of dial-in:
(adj) :
Of a system or service: accepting incoming connections over a telephone line.
(n) :
The act of connecting to a system or service by means of a telecommunication network.
(adj) :
(networking) Of a computer, set up to accept incoming modem calls.
(adj) :
Of a radio or television program: synonym of call-in.
(adj) :
(networking, proscribed) Dial-up.
(n) :
(drag racing) A driver's estimate of the time required to reach and cross the finish line, used to determine the head start for each vehicle.