ghast·ful \-fəl\adjective Etymology: Middle English gastful, from gast, gost spirit, ghost + -ful — more at ghost 1.obsolete: full of fear : frightened < the prelate saw their fall with ghastful eyes — John Ozell > 2.archaic: giving rise to fear : frightful < this ghastful dream … soon awoke him — John Lane fl1620 > • ghast·ful·ly\-fəlē\adverb, obsolete