Not in every dictionary… an adjective, pronounced in-ter-stes. 15th century Middle English, from Latin interstitium, from inter- + -stit, -stes standing (as in superstes standing over).

1 a: a space that intervenes between things; especially : one between closely spaced things (interstices of a wall)
b: a gap or break in something generally continuous (the interstices of society)

2 a short space of time between events