A bacchius () is a metrical foot of three syllables, consisting of one unstressed syllable followed by two stressed ones.
In accentual-syllabic verse we could describe a bacchius as a foot that goes like this:
Example:
When day breaks
the fish bite
at small flies.
The Christmas carol 'No Small Wonder' by Paul Edwards is a fair example of usage.
The name is thought to come from its use in ancient Greek songs to the god Bacchus.