ˈtrēd.ə(r), -ētə- noun
( -s )
Etymology: Middle English treyter, from Middle French traiteur, from traitier to treat, negotiate + -eur -or — more at treat
1. : one that negotiates terms of a settlement : negotiator
2.
[ treat (I) + -er ]
: one that treats: as
a. : one that treats materials (as timber, oil, or beer) with chemicals
b. : an apparatus (as an agitator) for treating materials