Tonic/ˈtɑːnɪk/ Definition 1 of 4Pro Tip 1/3Improves Health Use it to describe something that makes you feel physically better. This herbal tonic is great for digestion. Pro Tip 2/3Vitality Boost Suggests a quick boost in energy or well-being, often temporary. I need a tonic to get through this tiring day. Pro Tip 3/3Health Context Commonly used in health and wellness contexts or discussions. This tonic supports immune system function.