The practice of loading websites with a large number of keywords in an effort to affect a website's placement on search engine results pages is referred to as "keyword stuffing" by Google in its official definition of the term (SERPs).
These phrases, which Google also refers to as "irrelevant keywords," often occur in groupings, lists, or out of context, as the search engine giant points out. This last point is the one that, if done incorrectly, has the potential to irritate your target audience the most.
Preventing keyword stuffing
Alternate forms of a keyword that appears an excessive number of times should be used in its place if you want to prevent problems caused by improper optimization of keywords. There are several different online programs that can be used to build a list of terms that are synonymous with one another. However, while you are doing the synonym thing, you should still keep the target audience in mind. Using esoteric synonyms that immediately confuse readers is not going to do you any favors, and it won't help your writing either.
Utilizing the findings from your keyword research is another method that may help you avoid the practice of keyword stuffing in your content. Common research tools for keywords also have the capability of producing lists of relevant keywords for you.
After that, you'll have the ability to do an SEO keyword search across all of the listings. If you do this, you will be able to switch around similar terms a sufficient amount to reduce the need to repeat the same ones an excessive number of times. You will, however, continue to get an adequate amount of SEO leverage.
Last but not least, you are well on your way to success if you are already making use of long-tail keywords. If you're not already doing this, it's possible that this is one of the factors contributing to your keyword stuffing problems.