To rewrite or revise a written text; to adapt or alter a piece (e.g., a novel or script).
古い小説を現代語に書き改める作業はとても大変だ。
Rewriting an old novel into modern language is very demanding work.
監督の注文で脚本を何度も書き改めた。
I rewrote the script many times at the director's request.
誤字脱字を見つけて、該当部分を書き改めた。
I found typos and rewrote the relevant parts.