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Webster 1913 Edition

Adj.

Having three corners, or angles;

as, a

three-cornered

hat

(Bot.)

Having three prominent longitudinal angles;

as, a

three-cornered

stem

Adj.

[three and corner.]

Having three corners or angles; as a three-cornered hat.

In botany, having three sides, or three prominent longitudinal angles, as a stem.

three-cornered ‎(not comparable)