Spondee
A spondee is a metrical foot consisting of two long syllables, as determined by syllable weight in classical meters, or two stressed syllables in modern meters. The word comes from the Greek σπονδή, spondḗ, "libation".
The spondee typically does not provide the basis for a metrical line in poetry. Instead, spondees are found as irregular feet in meter based on another type of foot.
For example, the epics of Homer and Vergil are written in dactylic hexameter. This term suggests a line of six dactyls, but a spondee can be substituted in most positions. The first line of Virgil's Aeneid has the pattern dactyl-dactyl-spondee-spondee-dactyl-spondee:
In classical meter spondees are easily identified because the distinction between long and short syllables is unambiguous. In English meter indisputable examples are harder to find because metrical feet are identified by stress, and stress is a matter of interpretation.
For example, the first part of this line from Shakespeare's Troilus and Cressida would normally be interpreted as two spondees:
