The word antheridium 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™ Play In The Letters antheridium
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Seven Letter Word Alert: (53 words)
airtime, arenium, denarii, detrain, diamine, hairnet, handier, haunted, haunter, humaner, inditer, inertia, inherit, interim, intrude, manured, martini, matured, minaret, miniate, mintier, minuter, munited, muriate, natured, nitride, raiment, readmit, reaudit, rhenium, runtime, temurah, termini, thiamin, thunder, timider, tradein, trained, unaimed, unaired, unarmed, unearth, unhated, unheard, unmated, unrated, untamed, untimed, untired, untread, untried, uridine, urinate