/ˈhɑːrmfl/ (rather formal) ​causing damage or injury to somebody/something, especially to a person's health or to the environment.

causing damage or injury to someone or something, especially to a person's health or to the environment the harmful effects of alcohol the sun's harmful ...

There is one meaning in OED's entry for the adjective harmful. See 'Meaning & use' for definition, usage, and quotation evidence.

the fact of causing damage or injury to somebody/something, especially to a person's health or to the environment

​in a way that causes damage or injury to somebody/something, especially to a person's health or to the environment. Take your English to the next level. The ...

damage or injury that is caused by a person or an event He would never frighten anyone or cause them any harm. He may look fierce, but he means no harm.

​harm somebody/something to hurt or injure somebody or to damage something. He would never harm anyone. Pollution can harm marine life.

Evil (physical or otherwise) as done to or suffered by some person or thing; hurt, injury, damage, mischief. Often in the set phrase 'to do more harm than good' ...

harm to have a bad effect on someone or something's life, health, happiness, or chances of success:Pollution can harm marine life. damage, hurt, or harm? Hurt ...

HARMFUL definition: 1. causing harm: 2. causing harm: . Learn more.