interstitial

UK: /ˌɪntəˈstɪʃəl/ US: (in′tər stish′əl)

WordReference Random House Unabridged Dictionary of American English © 2025

in•ter•sti•tial  (in′tər stish′əl), adj. 

1. pertaining to, situated in, or forming interstices.
2. Anatomy situated between the cells of a structure or part:
   interstitial tissue.

n. 

3. [Crystall.] an imperfection in a crystal caused by the presence of an extra atom in an otherwise complete lattice. Cf. vacancy (def. 6).

• Latin interstiti(um) interstice + -al¹
• 1640–50

in′ter•sti′tial•ly, adv. 

Collins Concise English Dictionary © HarperCollins Publishers::

interstitial / ˌɪntəˈstɪʃəl/ adjective

1. of or relating to an interstice or interstices
2. forming or occurring in an interstice: an interstitial atom
3. occurring in the spaces between organs, tissues, etc: interstitial cells

noun

1. an atom or ion situated in the interstices of a crystal lattice

ˌinterˈstitially adverb