Lethal/ˈliːθl/ Definition 1 of 2Pro Tip 1/3Extreme Danger Use 'lethal' for something so dangerous it can kill, like poisons or weapons. Rattlesnake venom is lethal if not treated quickly. Pro Tip 2/3Health Risks 'Lethal' is often used to describe serious risks to health, even over time. Long-term exposure to asbestos is lethal. Pro Tip 3/3Not Hyperbole Avoid using 'lethal' in exaggeration, as it loses its strong impact of death. Calling a spicy meal 'lethal' is usually hyperbolic.