IPA: /ˈhiːd.fəl/
KK: /hid-fəl/
Being careful and attentive to something; showing awareness and consideration.
She was heedful of the advice given by her mentor.
Comparative: more heedful
Superlative: most heedful
Heedful is formed from "heed" (from Old English "hēdan", meaning to take care or pay attention) and "-ful" (meaning full of). The word "heedful" means full of care or attention.
Think of being 'full of care' or 'paying attention' — that's what heedful means.