IPA: /ɪɡˈnoʊbli/
KK: /ɪgˈnoʊbli/
In a way that is not honorable or noble; in a dishonorable manner.
He acted ignobly by betraying his friends for personal gain.
Ignobly is formed from "ignobilis" (meaning not noble) and the adverbial suffix "-ly" (meaning in a manner). The word describes actions done in a manner that is not noble or dishonorable.
Think of 'not noble' ('ignobilis') to remember that 'ignobly' means acting in a dishonorable way.