The word decertifying 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
Seven Letter Word Alert: (53 words)
centred, certify, citrine, cretify, cringed, deficit, definer, defying, deicing, deifier, dietine, dieting, dignify, dignity, dingier, edifice, edifier, editing, eidetic, enteric, enticed, enticer, feeding, feigned, feigner, fidgety, freeing, fringed, generic, genetic, ignited, igniter, incited, inciter, inditer, integer, niftier, nitride, nitrify, recited, rectify, reefing, refined, regency, reicing, reified, reigned, retying, rifting, tidying, tiering, tindery, treeing