in the Greek and Latin prosody, a poetical foot, consisting of a short syllable followed by a long one; as in

\[ \text{Syllaba longa brevi subiecta vocatur iambus, as Horace expresses it;} \] who also calls the iambus a swift, rapid foot, pes citus.

The word, according to some, took its rise from Iambus, the son of Pan and Echo, who invented this foot; or, perhaps, who only used sharp biting expressions to Ceres, when afflicted for the death of Proserpine. Others rather derive it from the Greek ἰάμβος, νενευμένος "poison;" or from ἰάμβος maledictus, "i rail, or revile;" because the verses composed of iambus's were at first only used in satire.