runtime Syllabification: (run·time)Pronunciation: /ˈrənˌtīm/Definition of runtime noun 1the time that a film or DVD lasts:a thriller that is so well paced it seems a lot shorter than its three-hour runtime 2 Computing the length of time a program takes to run. the time at or during which a program is run. a cut-down version of a program that can be run but not changed: you can distribute the runtime to your colleagues adjective (of software) in a reduced version that can be run but not changed. runtime in other Oxford dictionaries Definition of runtime in the British & World English dictionary