IPA: /ˌmʌltiˈsɛld/
KK: /mʌltiˈsɛld/
Having more than one cell; made up of multiple cells.
Humans are multicelled organisms, unlike bacteria which are unicellular.
Multicelled → It is formed from "multi-" (meaning many) and "cell" (from Latin "cella", meaning a small room or chamber). The word "multicelled" refers to an organism that is composed of many cells.
Think of 'many' ('multi-') small 'rooms' ('cella') coming together to form a living organism — that's what multicelled means.