Ignite/ɪɡˈnaɪt/ Definition 1 of 3Pro Tip 1/3Literal Fire Used when actually starting a fire, not just metaphorically speaking. Campers need to be careful not to ignite a forest fire. Pro Tip 2/3Immediate Start Implies that the fire or burning starts quickly or suddenly. A lightning strike can ignite trees instantly. Pro Tip 3/3Causation Emphasizes the action of causing something to burn, not the state of being on fire. He tossed his cigarette and accidentally ignited the dry brush.