The word mongrelise 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: 17
Highest Scoring Words With Friends™ Play In The Letters mongrelise
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Seven Letter Word Alert: (28 words)
elogies, eloigns, genomes, girnels, glories, greisen, gremlin, ignores, isomere, leering, legions, lingers, lingoes, mingler, mingles, mongers, mongrel, negroes, reeling, regimen, regimes, regions, relines, remiges, remines, seeming, semilog, slinger