A bacchius (/bəˈkəs/) is a metrical foot used in poetry.

Metrical feet and accents
Disyllables
◡ ◡pyrrhic, dibrach
◡ –iamb
– ◡trochee, choree
– –spondee
Trisyllables
◡ ◡ ◡tribrach
– ◡ ◡dactyl
◡ – ◡amphibrach
◡ ◡ –anapaest, antidactylus
◡ – –bacchius
– – ◡antibacchius
– ◡ –cretic, amphimacer
– – –molossus
See main article for tetrasyllables.

In accentual-syllabic verse we could describe a bacchius as a foot that goes like this:

da DUM DUM

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.