The Collaborative International Dictionary
Diiambus
Diiambus \Di`i*am"bus\, n. [NL., fr. Gr. ?; di- = di`s- twice + ?. See Lambus.] (Pros.) A double iambus; a foot consisting of two iambuses (? ? ? ?).
Wiktionary
diiambus
n. (context poetry English) A double iambus; a metrical foot consisting of two iambs.