(1) In word processing, the last line of a paragraph that appears as the first line of a page. Widows are considered bad form in page layout, so many word processors allow you to avoid them. When the word processor detects a widow, it can end the page one or more lines early so that at least the last two lines from the paragraph start the next page. Some word processors avoid widows by moving all the lines on the page closer together so that the last line can fit on the same page.
The converse of a widow is an orphan, the first line of a paragraph appearing as the last line of a page.
(2) The last line of a paragraph that is much shorter than all the other lines in the paragraph.