Generally; mostly; approximately — an adverb indicating an overall estimate or rough judgment.
だいたいの時間を教えてください。
Please tell me the approximate time.
だいたい終わったから、片付け始めよう。
It's almost finished, so let's start tidying up.
その計画はだいたい問題ないと思う。
I think that plan is generally fine.
General; rough — used as a noun (with の) to mean a general idea or rough outline.
まず大体の計画を立ててから詳細を詰めよう。
First make a rough plan, then work out the details.
大体の見当はついたが、確認が必要だ。
I have a rough idea, but it needs to be checked.
Outline; gist; main points — a noun meaning the essence or main substance of something.
会議の大体をメモにまとめておいてください。
Please summarize the main points of the meeting in a memo.
論文の大体が分かったら、序章を書き始めよう。
Once you understand the gist of the paper, start writing the introduction.
In the first place; first and foremost — used to indicate the starting point or priority.
大体、彼が来るかどうか確認してから進めよう。
First of all, let's confirm whether he's coming before we proceed.
大体、謝るべきは彼のほうだと思う。
To begin with, I think he's the one who should apologize.