The word mongrelising 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: 22
Highest Scoring Words With Friends™ Play In The Letters mongrelising
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Seven Letter Word Alert: (63 words)
elision, eloigns, gingers, ginseng, girlies, girling, girnels, girning, glories, gosling, gremlin, griming, ignores, inlines, inosine, ioniser, ironies, ironing, legions, lensing, lignins, limning, lingers, lingoes, linings, lionise, lionism, loggers, longing, merging, mingler, mingles, minions, mongers, mongrel, morning, niggler, noisier, onliner, origins, regions, reining, ringing, ringmen, rinsing, roiling, semilog, serging, sieging, signing, singing, sirloin, slimier, sliming, slinger, slogger, smilier, smiling, sniggle, snogger, snoring, soggier, soiling