IPA: /ˌmʌltiˈeɪdʒənsi/
KK: /mʌltiˈeɪdʒənsi/
Relating to or involving several different organizations or agencies working together.
The multiagency response to the disaster helped to coordinate efforts effectively.
Multiagency → It is formed from "multi-" (meaning many) and "agency" (from Latin "agens", meaning doing or acting). The word refers to the collaboration of many agencies working together to achieve a common goal.
Think of 'many' ('multi-') groups or organizations 'acting' ('agency') together — that's what multiagency means.