IPA: /ˈɡaɪl.fəl.nəs/
KK: /ˈɡaɪl.fəl.nəs/
The quality of being deceitful or cunning, often in a way that is clever but not honest.
His guilefulness made it difficult for others to trust him.
Guilefulness is formed from "guile" (from Old French *guile*, meaning deceit or trickery) and "-fulness" (meaning the state of being full of). The word describes the state of being full of deceit or trickery.
Think of 'guile' meaning deceit, and '-fulness' indicating a state of being. This helps you remember that guilefulness refers to being full of deceit.