IPA: /ˌprɛpəˈzɛʃən/
KK: /prɛpəˈzɛʃən/
A belief or opinion that someone has before they have all the facts, often leading to bias or unfair judgment.
Her prepossession about the new student made her treat him unfairly.
Prepossession is formed from "pre-" (meaning before) and "possession" (from Latin "possidere", meaning to hold or occupy). The word refers to the state of having something before others or having a prior claim to it.
Think of having something 'before' ('pre-') you actually own it ('possession'). This helps you remember that prepossession means having a prior claim or hold on something.