What is the meaning of the word deleterious?

The definition of deleterious is something that is harmful or damaging. Moreover, if something is deleterious, it often makes things worse. For example, smoking often has obvious deleterious effects on a person's health, not to mention his or her social life.

To note more examples, parents will worry that their divorce will have a deleterious effect on their kids, but in the end it may be less harmful than the kids watching them fight all the time. Next, for most plants, a lack of sunlight has very deleterious consequences, but there are still some plants that actually do very well in the dark. Lastly, it's a wonder, given how well established the science is, that people continue to do things that are deleterious to the world's fragile ecosystem. Everyone must be willing to live with the deleterious (harmful) effects.