Broad Outline
Outline, Overview
noun
たいりゃく
大略 （たいりゃく） Broad Outline, Outline, Overview
概要 （がいよう） Outline, Summary
輪郭 （りんかく） Outline, Border, Silhouette, Summary, Features, Appearance
大概 （たいがい） In General, Mainly, Mostly
A Summary 大略 is like a big 大 abbreviation 略
Big just means "a lot" in this case. A Summary/Outline explains what happened with a lot of abbreviation.