The word cautiousness 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: 18
Highest Scoring Words With Friends™ Play In The Letters
Seven Letter Word Alert: (48 words)
aconite, actions, ascents, ascites, assents, atonics, auction, aunties, caisson, caseins, casinos, cassons, cations, caution, cession, consist, cosiest, cosines, cousins, incests, insects, nosiest, notices, nutcase, octanes, oecists, osseins, sanctus, seasons, secants, section, seitans, session, sestina, siestas, sinuate, sinuous, sinuses, stances, suction, sunsets, sustain, tenuous, tissues, tocsins, toucans, unseats, unstoic