ˈkəplə(r) noun
( -s )
1.
a. : one that couples (as a link, ring, or shackle that connects cars or the ends of a chain belt)
b. : coupling
c. : a contrivance on a keyboard instrument by which any two or more of the manuals or a manual and the pedal keyboard or keys of the same keyboard an octave apart are connected so as to act together when one is played
d. : a radio device coupling two electric circuits
e. : an agent (as a mutual solvent) that renders two nonmiscible liquids miscible or aids in the formation of emulsions (as of oils in soap solutions) — called also coupling agent
2. : a compound in a color-photography emulsion or developer solution that combines with the oxidized developer to form a dye — compare color developer