wail·ful \ˈ ̷ ̷_fəl\adjective 1.: expressing grief or pain : sorrowful, mournful < tangle her desires with wailful sonnets — Shakespeare > 2.: uttering a sound suggestive of mourning or wailing < the wailful bagpipes > < the wailful sough of the wind through the trees > • wail·ful·ly\-fəlē, -li\adverb