六芒星形
六线形

[ noun ]
a regular polygon formed by extending each of the sides of a regular hexagon to form two equilateral triangles
<noun.shape>

Hexagram \Hex"a*gram\, n. [Hexa- + -gram.]
A figure of six lines; specif.:
(a) A figure composed of two equal triangles intersecting so
that each side of one triangle is parallel to a side of
the other, and the six points coincide with those of a
hexagon.
(b) In Chinese literature, one of the sixty-four figures
formed of six parallel lines (continuous or broken),
forming the basis of the I Ching (Yih King), or ``Book of
Changes.'' --S. W. Williams.
[Webster 1913 Suppl.]