Occurring in interstices or spaces; cells within tissues.
- A dictionary of scientific terms. By Henderson, I. F.; Henderson, W. D. Published 1920. (adjective) (adj.) (adjective)
Pertaining to or containing interstices.
- Nuttall's Standard dictionary of the English language. By Nuttall, P.Austin. Published 1914. (adjective) (adj.) (adjective)
Pert. to or containing interstices.
- Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874. (adjective) (adj.) (adjective)
Lying between.
- Warner's pocket medical dictionary of today. By William R. Warner. Published 1898. (adjective) (adj.) (adjective)

Usage examples:

In the embryo the interstitial gland is large, in the adult proportionately small.
- Hormones and Heredity by J. T. Cunningham
How remarkably these interstitial cells influence the entire structure and vitality of the organism is indicated by these facts.
- The Glands Regulating Personality by Louis Berman, M.D.
So also there are the minor and interstitial trades that are still carried on by handicraft methods; these, too, are still somewhat loosely held in the fabric of the business system.
- An Inquiry Into The Nature Of Peace And The Terms Of Its Perpetuation by Thorstein Veblen