The word philatelists 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: 19
Highest Scoring Words With Friends™ Plays In The Letters philatelists
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Seven Letter Word Alert: (35 words)
aplites, ashiest, atheist, elitist, halites, hapless, haplite, hatless, illites, latites, liaises, lipases, lipless, pallets, palsies, pastels, pasties, patties, pettish, pietist, pilates, pistils, pitless, plashes, spittle, stalest, staples, stealth, stipite, tallest, tallies, tallish, theists, thistle, tipless