n. /kown"teuhr stayn'/ ; v. /kown'teuhr stayn"/ , Histol. n.
1. a second stain of a different color applied to a microscopic specimen and used to color and contrast those parts not retaining the first stain.
v.t.
2. to treat (a microscopic specimen) with a counterstain.
v.i.
3. to become counterstained; take a counterstain.
[ 1890-95; COUNTER- + STAIN ]