11 letters · 19 points in Scrabble
adjective not producing desired results; wasteful
adjective lacking the ability or skill to perform effectively; inadequate
originEtymology tree Proto-Indo-European *né Proto-Indo-European *n̥- Proto-Italic *n̥- Latin in-bor. Middle English in- English in- English efficient English inefficient From in- + efficient.
Etymology from Wiktionary, CC BY-SA 3.0