[in.ter.sti.tial] adj (1646) 1: relating to or situated in the interstices
2. a: situated within but not restricted to or characteristic of a particular organ or tissue--used esp. of fibrous tissue b: affecting the interstitial tissues of an organ or part
3: being or relating to a crystalline compound in which usu. small atoms or ions of a nonmetal occupy holes between the larger metal atoms or ions in the crystal lattice -- in.ter.sti.tial.ly adv