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Webster 1913 Edition

Adj.

[See

Divided into three parts, or into threes; three-forked;

as, a

trichotomous

stem

Martyn.

Adj.

[See Trichotomy.] Divided into three parts, or divided by threes; as a trichotomous stem.

trichotomous ‎(not comparable)

Divided into three parts, or into threes; forking three ways.
A trichotomous stem. — Martyn.