The word overwintering 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: 24
Highest Scoring Words With Friends™ Play In The Letters overwintering
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Seven Letter Word Alert: (52 words)
entwine, environ, evening, eviting, griever, grinner, igniter, ignitor, inerter, ingrown, integer, intoner, intwine, invitee, inviter, invitro, inwoven, ironing, nervier, nerving, nitrene, overwet, reeving, regrown, reigner, reining, reinter, renting, retwine, rewoven, rewrite, rewrote, rioting, riveter, tiering, tinnier, treeing, twining, veering, veinier, veining, venting, vertigo, vetoing, viewing, vintner, vitrine, weening, wonting, wringer, writing, wronger