triplex(s = adj.all) ternary, treble, triple - having three units or components or elements; "a ternary operation"; "a treble row of red beads"; "overcrowding made triple sessions necessary"; "triple time has three beats per measure"; "triplex windows"

   Having three principal operative parts or motions, so as to produce a three-fold effect. [Webster 1913 Suppl.]

triplex, adj. & n.
--adj. triple or threefold.
--n. (Triplex) Brit. propr. toughened or laminated safety glass for car windows etc.

Etymology:
L triplex -plicis (as TRI-, plic- fold)