from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. Divided into three parts, or into threes; forking three ways.
from the GNU version of the Collaborative International Dictionary of English
- adj. Divided into three parts, or into threes; three-forked.
from The Century Dictionary and Cyclopedia
- Divided into three parts, or divided by threes; branching or giving off shoots by threes; trifurcate; also, dividing a genus into three species.
trichotomy + -ous? (Wiktionary)