The main point or general outline of something; the gist or basic points rather than detailed specifics.
会議の大筋はすでに決まっているので、細かい調整だけ行いましょう。
The main points of the meeting have already been decided, so let's just make some minor adjustments.
小説の大筋を友達に話したら、ネタバレになると言われた。
When I told my friend the gist of the novel, they said it would be a spoiler.
まずは大筋を把握してから、詳細に入ったほうが効率的だ。
It's more efficient to grasp the general outline first and then get into the details.