IPA: /əˈkwɛɪntɪd/
KK: /əˈkwāntəd/
Having knowledge of or being familiar with someone or something.
I am well acquainted with the rules of the game.
Acquainted is formed from "ac-" (a variant of "ad-", meaning to) and "quaint" (from Latin "cognitus", meaning known). The word describes the state of being made known to someone or something, hence being familiar with it.
Think of 'being made known to' someone or something — 'ac-' means to, and 'quaint' relates to knowing. This helps you remember that 'acquainted' means being familiar with someone or something.