► harmfulcausing harm, or likely to cause harm: The harmful effects of smoking are well known. Wash the fruit to remove harmful bacteria.
► poisonous containing a substance that can kill you or make you sick if you eat it, breathe it, etc.: She was bitten by a poisonous snake and had to go to the hospital.
► toxic poisonous. Used especially about chemicals: Burning tires produces toxic fumes.
► damaging causing physical damage or harmful effects: The researchers are studying the damaging effects of alcohol on the brain.
► detrimental formal harmful or damaging to something: Fatty foods are detrimental to your health.
► destructive causing something to be destroyed: A large population of deer can be very destructive to woodlands.
► deleterious formal damaging or harmful: The treatment is supposed to reverse some of the deleterious effects of aging.