IPA: /ɪˈlɪsɪtli/
KK: /ɪˈlɪsɪtli/
In a way that is not allowed by law or rules; done illegally or unethically.
He was caught selling drugs illicitly.
Illicitly → It is formed from "illicit" (from Latin "illicitus", meaning not permitted or unlawful) and "-ly" (a suffix used to form adverbs). The word "illicitly" means in a manner that is not allowed or unlawful.
Think of something that is 'not permitted' ('illicit') and remember that doing it 'illicitly' means doing it in a way that is against the rules.