The word multivariate 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: 21
Highest Scoring Words With Friends™ Plays In The Letters multivariate
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Seven Letter Word Alert: (28 words)
airmail, airtime, amateur, ilvaite, imitate, limiter, maltier, marital, marlite, martial, militar, muriate, rattail, reavail, rivulet, tertial, titular, travail, tritium, trivial, uraemia, uralite, valuate, variate, vaulter, velaria, virtual, vitiate