IPA: /ˈfɔːməlaɪz/
KK: /ˈfɔrməˌlaɪz/
To make something official or to give it a formal status.
The committee decided to formalise the new rules for the competition.
Past: formalised
Past Participle: formalised
Formalise → It is formed from "formalis" (from Latin, meaning pertaining to form) and "-ize" (a suffix used to indicate to make or to become). The word "formalise" means to make something formal or to give it a specific form.
Think of giving something a specific 'form' ('formalis') — that's why to 'formalise' means to make it formal.