The word tertiaries 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: 10
Highest Scoring Words With Friends™ Plays In The Letters
Seven Letter Word Alert: (29 words)
aeriest, airiest, artiest, artsier, attirer, attires, iratest, irisate, iterate, ratters, rattier, rearise, restart, restate, retaste, retears, retires, retreat, retries, seriate, serrate, starter, striate, tarries, tastier, tearers, tearier, testier, treater