The word invariableness is playable in Words With Friends™, no blanks required. Because it is longer than 7 letters, you would have to play off an existing word or do it in several moves.
Words With Friends™ Letter Score: 24
Highest Scoring Words With Friends™ Play In The Letters invariableness
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Seven Letter Word Alert: (98 words)
abasers, abrases, abseils, aerials, airable, airbase, airless, airline, alanine, aliases, alibies, aniline, anneals, arabise, arsenal, asinine, baleens, banaler, banners, basilar, beanies, beavers, beslave, biennia, blesser, braises, braless, earless, enabler, enables, enliven, enseals, ensears, enslave, ensnare, ensnarl, enviers, inlines, insaner, inverse, laveers, leaners, leasers, leavens, leavers, lesbian, liaises, nabales, nailers, nirvana, raisins, ravines, realise, reavail, rebales, rebases, rebless, relines, relives, renails, resails, resales, resaves, reseals, reveals, reviles, revises, ribless, risible, sailers, salines, salivas, salvers, salvias, savable, sealers, serials, servals, servile, several, siennas, silanes, silvans, silvers, sinners, slavers, sleaves, slivers, snivels, veilers, veilier, veinier, velaria, veneral, verbals, verbena, versine, visible