IPA: /ˈrænsækər/
KK: /ˈrænˌsækər/
A person who searches through a place in a messy or violent way, often to steal things.
The ransacker left the house in disarray after searching for valuables.
Ransacker is formed from "ran" (from Old English "rān", meaning to plunder or rob) and "sacker" (from Old French "sacquer", meaning to sack or loot). The word describes someone who plunders or robs, particularly by searching through and taking valuables from a place.
Think of someone 'plundering' ('ran') and 'sacking' ('sacker') a place — that's why ransacker means a person who robs or loots.