The word femtoseconds 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: 23
Highest Scoring Words With Friends™ Play In The Letters
Seven Letter Word Alert: (30 words)
cements, cenotes, cestode, comedos, condoms, confess, defects, dements, demotes, denotes, densest, descent, dotcoms, encodes, endmost, festoon, foments, fondest, footmen, nosodes, octenes, osteons, scented, scooted, seconds, snooted, softens, someone, soonest, stenose