Pyrrhic monometer
(also pyrrhic dimeter, trimeter, tetrameter, pentameter, hexameter, heptameter and octameter)
A pyrrhic foot has a short syllable followed by another short syllable (SS or UU).
Imagine repeating this line after line, whether once per line (monometer), eight times per line (octameter) or any number of lines in between, and you would have a particularly monotonous poem
Like spondees (two long syllables, LL or //), pyrrhic feet are used along with other types of foot in the same line, to provide rhythmic variation.
Examples
In this line from Andrew Marvell's poem, The Garden, there are two pyrrhic feet (that we show here in bold type):
To a green thought in a green shade.
A closer look at the feet in this line
U = short syllable; / = long syllable; | = division between feet
Another example is this line from Lord Byron's poem, Don Juan:
My way is to begin with the beginning.
A closer look at the feet in this line
U = short syllable; / = long syllable; | = division between feet