By thy triple shape as thou art seen. Dryden.

Triple crown, the crown, or tiara, of the pope. See Tiara, 2. -- Triple-expansion steam engine, a compound steam engine in which the same steam performs work in three cylinders successively. -- Triple measure (Mus.), a measure of tree beats of which first only is accented. -- Triple ratio (Math.), a ratio which is equal to 3. -- Triple salt (Chem.), a salt containing three distinct basic atoms as radicals; thus, microcosmic salt is a triple salt. -- Triple star (Astron.), a system of three stars in close proximity. -- Triple time (Mus.), that time in which each measure is divided into three equal parts. -- Triple valve, in an automatic air brake for railroad cars, the valve under each car, by means of which the brake is controlled by a change of pressure in the air pipe leading from the locomotive.