The word unimaginable 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 unimaginable
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Seven Letter Word Alert: (34 words)
alanine, albumen, albumin, alumina, alumnae, ambling, amiable, anginal, aniline, bailing, beaming, biennia, blaming, blueing, bulimia, geminal, gmelina, guanine, imagine, lambing, laminae, leaning, legumin, limning, lineman, mailbag, mailing, mauling, meaning, melanin, nailing, numbing, unagile, unalign