in-service adjective 2verb 1in service prepositional phrase 2forms 3 adjective2 •Taking place when one is an employee.To sensitize their staffs, ASOs can offer in-service trainings about incest and its impact on unsafe sex and other high-risk behavior, both to professionals and to peer-educators. — 1991 •Relating to or being a full-time] employee.We offer both in-service and full-time employee training. verb1 •To train or educate (someone) while they are working; to give on-the-job training to.She spends most of her time in-servicing teachers in helping struggling students. in service prepositional phrase2 •Available for use; operational.About 20,600 Vélib’ bicycles are in service here, with more than 1,450 self-service rental stations. — 2008 •(UK) Employed as a domestic servant. formsin-serviced · in-servicing · in-services