IPA: /ˈɡaɪləs/
KK: /ˈɡaɪləs/
Someone who is honest and straightforward, without any deceit or trickery.
Her guileless nature made her very trustworthy among her friends.
Guileless is formed from "guile" (from Old French *guile*, meaning deceit or trickery) and "-less" (meaning without). The word describes a state of being without deceit or trickery, indicating innocence or straightforwardness.
Think of being 'without' ('-less') 'deceit' ('guile') — that's why guileless means innocent or straightforward.