Using keywords over and over again without any meaning is called Keyword stuffing. It is an unethical practice of SEO. It may get your website spammed. Google may impose a penalty or your website can be de-indexed by this practice. Keyword stuffing is not liked by the crawler. It is as if you are imposing your keywords forcefully on your web page.
You know that you can use 125 characters in the title. What if you consume all character limits by just putting your keyword again and again in the title.
An Example of Keyword Stuffing
<title>keyword stuffing, stuff Keyword…………………………….Stuffing Keyword</title>
This is called keyword stuffing. It can make the wrong effect and your website ranking can be down.