In Greek and Latin poetry, a choriamb /ˈkɔːriˌæmb/ (Ancient Greek: χορίαμβος - khoriambos) is a metron (prosodic foot) consisting of four syllables in the pattern long-short-short-long (— ‿ ‿ —), that is, a trochee alternating with an iamb.
Choriambs are one of the two basic metra[1] that do not occur in spoken verse, as distinguished from true lyric or sung verse.
[2] The choriamb is sometimes regarded as the "nucleus" of Aeolic verse, because the pattern long-short-short-long pattern occurs, but to label this a "choriamb" is potentially misleading.
[3] In the prosody of English and other modern European languages, "choriamb" is sometimes used to describe four-syllable sequence of the pattern stressed-unstressed-unstressed-stressed (again, a trochee followed by an iamb): for example, "over the hill", "under the bridge", and "what a mistake!".
In English, the choriamb is often found in the first four syllables of iambic pentameter verses, as here in Keats' To Autumn: