strike

means the partial or complete concerted refusal to render service, or the retardation or obstruction of the rendering of service, or failure to serve, by members of the Defence Force or any auxiliary service for purposes of protest, petition or remedying a grievance or resolving a dispute in respect of any matter of mutual interest between the employer and such members, and every reference to 'serve' in this definition includes overtime, service or duty, whether it is voluntary or compulsory;