interstitial
in.ter.sti.tial \.int-*r-'stish-*l\ \-*-le-\ aj 1: relating to or situated in the interstices 2a: situated within but not restricted to or characteristic of a particula r organ or tissue - used esp. of fibrous tissue 2b: affecting the interstitial tissues of an organ or part - in.ter.sti.tial.ly av