godan verb (-u), transitive verb
Used when a character, word, or sentence is written with a mistake, such as a wrong kanji or a slip of the pen.
漢字を書き損なって、何度も書き直した。
I miswrote the kanji and rewrote it many times.
急
I was in a hurry, so I ended up writing the address incorrectly.
godan verb (-u), transitive verb
spoil by writing mistakes; ruin a written piece
Refers to ruining a letter, document, or other written work because of writing errors, often requiring a fresh start. The focus is on the result being spoiled, not just a single mistake.
最後の行で書き損なって、手紙を最初から書き直した。
I made a writing mistake on the last line and had to rewrite the letter from the beginning.
清書のときに書き損なうと、とてもがっかりする。
When you spoil a fair copy by a writing mistake, it's really disappointing.