Definition of "interstitial"

The outer surface is covered with variable amounts of dental plaque and saliva. The inner surface is bathed in interstitial fluid or lymph.

1965, Jerome F. Fredrick, Murray L. Schole, Mechanisms of Dental Caries, page 761

That he ran the risk of blowing out the stained-glass windows was of no consequence since no one liked them anyway, and the paper mill fumes were gnawing at the interstitial lead.

1999, Neal Stephenson, Cryptonomicon

The interstitial fluid is located between cells and the capillaries. This fluid provides a bridge between the fluid in the intravascular compartment and the intracellular compartment. Chemicals in the blood must pass through the interstitial fluid if they are to reach cells.

2011, Chris Mulryan, Acute Illness Management, page 27

Whitney is absorbed especially by Dublin's unglamorous interstitial zones: the new housing estates and labyrinths of roads, watercourses and railways where the city peters into its commuter belt.

2014 August 23, Neil Hegarty, “Hidden City: Adventures and Explorations in Dublin by Karl Whitney, review: 'a necessary corrective' [print version: Re-Joycing in Dublin, p. R25]”, in The Daily Telegraph (Review)‎

Interstitials should be used sparingly. Display an ad only the first time the user accesses a piece of content, not every time.

2007, Barbara Ballard, Designing the Mobile User Experience, page 126

The second mechanism, which is the primary focus of the present paper, involves insertion of interstitials into dangling bonds at the surface.

2008, E. G. Seebauer et al., Defect Engineering for Ultrashallow Junctions using Surfaces, in P. J. Timans, E. P. Gusev, H. Iwai, D.-L. Kwong, M. C. Öztürk, F. Roozeboom (editors), Advanced Gate Stack, Source/Drain, and Channel Engineering for Si-Based CMOS 4: New Materials, Processes, and Equipment, ECS Transactions: Volume 13, Issue 1, page 56