Authors who reuse portions of text that have appeared in one of their earlier published papers run the risk of being accused of:

Self-plagiarism.

Explanation:

Plagiarism is a serious business. It occurs when you take somebody's words or texts without citing them first, and thus you present them as your own words or texts, which is forbidden in the academic world. However, it may also occur that you take your own portions of text that you have used previously in another paper. If you don't cite yourself, this is also a type of plagiarism known as self-plagiarism.