An antibacchius is a rare metrical foot used in formal poetry. In accentual-syllabic verse an antibacchius consists of two accented syllables followed by one unaccented syllable. Its opposite is a bacchius. Example: ...
• (n.) A foot of three syllables, the first two long, and the last short (#).
An`ti·bac·chi'us noun [ Latin , from Greek ... + .... See Bacchius .] (Pros.) A foot of three syllables, the first two long, and the last short . 
a foot of three syllables that in quantitative meter consists of two long syllables followed by a short one, and that in accentual meter consists of two stressed syllables followed by an unstressed one. Cf. bacchius.