n. A bicycle for three riders.n. A collection or combination of three of a kind, or three united.n. In poetry, three verses or lines riming together.n. In music, a group of three tones to be performed in the time of two or four. Such groups are marked. . Compare sextuplet, decimole, etc.n. A combination of three plano-convex lenses in a compound microscope, which serves to render the object clear and distinct, and free from distortionāan improvement upon the doublet (see doublet, 2); also, a hand-microscope consisting of three double-convex lenses.n. In mathematics, a system of three families of surfaces such that one of each family passes through each point of space.n. One of three children born at one birth.n. plural Three links of chain, generally used to connect the cable with the anchor-ring.