RhymeZone: interdental definitions

Definitions of interdental:

adjective: Pertaining to the space between the teeth.
adjective: (phonetics) Pronounced with the tongue between the top and bottom teeth.
noun: (phonetics) A speech sound pronounced with the tongue between the top and bottom teeth.
noun: (dentistry) A small toothbrush for cleaning in between adjacent teeth.

(Definitions from Wiktionary)