n.
Pronunciation: ' t ō -n ə r
Function: noun
Date: 1888
: one that tones or is a source of tones: as a : a solution used to impart color to a silver photographic image b : a substance (as a thermoplastic powder) used especially to develop an image (as a latent xerographic image) on a piece of paper c : a liquid cosmetic for cleansing the skin and contracting the pores