From plain + -ful. <span class="searchmatch">plainful</span> (comparative more <span class="searchmatch">plainful</span>, superlative most <span class="searchmatch">plainful</span>) (archaic) Full of lamentation. 1780, John Bell, Bell's British Theatre:...
<span class="searchmatch">plainfuls</span> plural of <span class="searchmatch">plainful</span>...
painfull (comparative more painfull, superlative most painfull) Archaic spelling of painful. <span class="searchmatch">plainful</span>...