I. ˈtriməd.ə(r) noun
Etymology: Latin trimetrus, from Greek trimetros, from tri- three + metron measure — more at tri- , measure
: a line of three measures consisting of three dipodies (as in classical iambic, trochaic, and anapestic verse) or three feet (as in modern English verse)
II. adjective
: having three measures in a foot