The word mongrelizing 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: 31
Highest Scoring Words With Friends™ Play In The Letters mongrelizing
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Seven Letter Word Alert: (23 words)
girling, girning, glozing, gremlin, griming, ionizer, ironing, limning, lionize, longing, merging, mingler, mongrel, morning, niggler, onliner, reining, ringing, ringmen, roiling, zeroing, zingier, zinging