cinereous /sɪˈnɪəɹi.əs/ adjective3 •Of an ash-gray colour.With a bill two inches and a half long , very slender , and a little recurvated : head , and upper part of neck , cinereous , with dusky lines : over each eye a white line — 1784 •Like ashes. •Containing ashes. formsmore cinereous · most cinereous