Gruelling/ˈɡruːəlɪŋ/ Definition 1 of 1Pro Tip 1/3Physical Endurance Indicates activities that test your physical abilities to their limits. He endured a gruelling hike up the mountain. Pro Tip 2/3Emotional Intensity Can describe situations that are mentally or emotionally stressful. Surviving the gruelling interview process required resilience. Pro Tip 3/3Time Length Often used for tasks that take a long time and involve sustained effort. The team went through a gruelling eight-hour strategy session.