The word rainforest 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: 14
Highest Scoring Words With Friends™ Play In The Letters
Seven Letter Word Alert: (41 words)
antsier, artsier, atoners, errants, fainter, fairest, fireant, foister, forints, forties, fraters, froster, insofar, ironers, nastier, norites, orients, ornater, otarine, rafters, ranters, rations, refrain, reroast, restain, retains, retinas, retrain, rioters, roaster, roister, senator, snifter, snorter, stainer, stonier, tarries, terrain, trainer, treason, triones