Noxious is an adjective that describes something that is harmful, unpleasant or dangerous. It can refer to a substance that causes physical discomfort or injury when it comes into contact with human skin or is inhaled, such as poisonous chemicals or strong odors. In a broader sense, noxious can also describe things that are offensive or objectionable, like noise pollution or hate speech. The word originates from the Latin term "noxius," meaning "shameful" or "disgraceful."