the GNU version of the Collaborative International Dictionary of English
adj. Of or pertaining to a trisyllable; consisting of three syllables.
The Century Dictionary and Cyclopedia
Pertaining to a trisyllable; consisting of three syllables; as, a trisyllabic word or root.
Word Usage
"That verse wherein the accent falls on every third syllable, may be called trisyllabic verse; it is equivalent to what has been called anapestic; and we will still use the term anapest to express two unaccented and one accented syllable."