noun
slip of the pen; mistake in writing
Refers to an error made while writing by hand, such as a misspelling or wrong character.
年賀状に書き損じがあって、何枚か無駄にしてしまった。
I made some mistakes writing New Year's cards and wasted a few of them.
noun
something ruined by a writing mistake
Often used for items like postcards or forms that become unusable because of a slip of the pen.
書き損じのハガキは郵便局で交換してもらえます。
You can exchange spoiled postcards at the post office.