Final answer:
A widow is the term for the first line of a paragraph that prints as the last line on a page, creating an undesired visual gap.
Step-by-step explanation:
When the first line of a paragraph prints as the last line on a page, it is called a widow. Widows are considered undesirable in typesetting and page layout because they can create an awkward visual gap at the bottom of a page. To avoid such issues in documents, word processors like Microsoft Word offer formatting options to control text flow, including the use of paragraph indentation. For instance, when formatting, one might begin each entry at the left margin, and indent subsequent lines one-half inch, which can be done by selecting "Hanging" from the Special options on the Indentation section of the Paragraph menu.