IPA: /dɪˈsiːtfəlɪ/
KK: /dɪˈsitfəlɪ/
In a way that is intended to trick or mislead someone.
He deceitfully hid the truth from his friends.
Deceitfully → It is formed from "deceit" (from Old French *deceite*, meaning deception or trickery) and "-fully" (meaning in a manner full of). The word "deceitfully" means in a manner full of deceit or trickery.
Think of 'deceit' as trickery and remember that 'deceitfully' means acting in a manner full of trickery.