in a nutshell

Adverb

idiomatic

(idiomatic) In summary; briefly or simply.

Japanese Meaning

要約すると / 簡潔に言えば / 端的に言えば

In a nutshell, the project failed because we underestimated the time required.

要するに、そのプロジェクトは必要な時間を過小評価したため失敗しました。

Sense（1）

(idiomatic) In summary; briefly or simply.

He had a lot to say, but his answer, in a nutshell, was no.