1. relating to gaps: forming, situated in, or relating to one or more small openings, gaps, or cracks
[15th century. Via French - Latin interstitium intersistere, literally "stand still in the middle" sistere "cause to stand" stare "to stand"]
interstitial. Encarta® World English Dictionary [North American Edition] © & (P)2007
http://encarta.msn.com/dictionary_1861622011/interstitial.html (accessed: November 21, 2008).
Bob hated working as a projectionist; the junk they were pawning off as movies was bad enough, but listening to those idiots discuss them as they left the theater was worse. That was, until late one night, Bob spliced his own images in the interstitial moments between frames - not long enough to be noticed consciously, but long enough that the subconscious would picked them up.
Sitting through the 'bombs and bimbos' films was still difficult, but the conversation afterward sounded wonderfully intelligent. Bob could not wait to splice in ever more interesting vocabulary words to future films.