cuneate

Etymology
Borrowed from.

Adjective

 * 1)  wedge-shaped.
 * 2)  wedge-shaped, with the narrow part at the base.
 * 3)  having straight, or almost straight sides meeting at the apex or base.

Usage notes
A deltoid organ is roughly triangular in shape, but may have much less obvious "angles". An obdeltoid one is practically the same, except that the cuneate leaf's angle are better defined. Being cuneate does not prevent being sagittate.