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Webster 1913 Edition

Noun.

One who, or that which, whitens; a bleaching agent; a bleach; a bleacher; a blancher; a whitewasher.

Noun.

One who bleaches or makes white.

whitener ‎(plural whiteners)

Any substance used to whiten something; a bleach.
A person employed to whiten or bleach.
(Canada) A powder added to tea or coffee in place of milk. A "non-dairy creamer".

powder added to tea or coffee in place of milk