Summary
Outline
noun
The big abbreviation is where you take everything and abbreviate it down to show the big picture. This abbreviation is the summary or outline of something bigger.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
まずは事件の大略を説明してくれないか？
Can you explain the outline of the incident first?