choriambus
Concise Oxford English Dictionary © 2008 Oxford University Press:
choriambus /ˌkɒrɪˈambəs/
▶noun (pl. choriambi /-bʌɪ/) Prosody a metrical foot consisting of two short (or unstressed) syllables between two long (or stressed) ones.
– derivatives
choriambic adjective.
choriambic adjective.
'choriambus' also found in these Oxford entries:

