The Collaborative International Dictionary of English v.0.48:
Interspersion \In`ter*sper"sion\, n. The act of interspersing, or the state of being interspersed. InterspinalWordNet (r) 3.0 (2006):
interspersion n 1: the act of combining one thing at intervals among other things; "the interspersion of illustrations in the text" [syn: interspersion, interspersal]