interstitial space

noun4

1. •
   An in-between space.
2. •
   (architecture) The gaps between buildings/floors in architecture, used for systems and movement; the neglected or overlooked spaces between built structures, like alleys, courtyards, or empty lots.
3. •
   (anatomy) The fluid-filled area between cells in tissues (interstitium).
4. •
   (sociology) The informal, transitional zones where people from different groups or fields (e.g., hobbyists, professionals) interact.