The word inconvertibility cannot be made in Words With Friends™. It is 16 letters long, too long to fit on a WordsWithFriends board (15 letters max).
Highest Scoring Words With Friends™ Plays In The Letters inconvertibility
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Seven Letter Word Alert: (60 words)
binocle, biolite, biotite, bitcoin, bittier, blotter, bonnier, bonnily, bottler, brevity, brittle, byliner, citrine, cittern, clitter, clotter, connive, content, convent, convert, cornett, cornily, environ, evictor, inciter, incline, inertly, inocyte, intoner, inviter, invitro, invoice, lection, liberty, lintier, lottery, niobite, nitrite, nittier, nonevil, novelty, olivine, onliner, overbit, overlit, overtly, ovinely, retinol, tinnier, tinnily, tintier, titivil, trilobe, trinity, viceroy, victory, vintner, violent, vitrine, vitriol