godan verb (-su)
expand a text; lengthen a piece of writing
Used when a writer intentionally adds content to make a text longer, such as padding an essay or expanding a draft.
字数が足りなかったので、レポートを書き伸ばした。
The word count was short, so I expanded the report.
彼は短いメモを書き伸ばして
He expanded the short memo into a detailed explanation.