IPA: /ˌɪlɪˈdʒɪtəmətli/
KK: /ɪlɪˈdʒɪtəmətli/
In a way that is not allowed by law or rules; unlawfully or improperly.
He was accused of acting illegitimately in the business deal.
Illegitimately → It is formed from "il-" (meaning not), "legitimus" (meaning lawful or legitimate), and "-ly" (meaning in a manner). The word describes an action that is not done in a lawful or legitimate manner.
Think of 'not' ('il-') and 'lawful' ('legitimus') to remember that 'illegitimately' means acting in a way that is not lawful.