bi ‧ o ‧ in ‧ di ‧ ca ‧ tor /ˌbaɪəʊˈɪndəkeɪtə, ˌbaɪəʊˈɪndɪkeɪtə $ ˌbaɪoʊˈɪndəkeɪtər/ BrE AmE noun [countable] technical
a small number of animals, plants, insects etc that are typical of all the animals, plants etc normally found in a particular area, which scientists study in order to get information about the whole area:
This insect-bacteria bioindicator is a reliable tool for assessing environmental damage to the country’s wetlands.