The Collaborative International Dictionary of English v.0.48:

Ancipital \An*cip"i*tal\, Ancipitous \An*cip"i*tous\, a. [L.
   anceps, ancipitis, two-headed, double; an- for amb- on both
   sides + caput head.] (Bot.)
   Two-edged instead of round; -- said of certain flattened
   stems, as those of blue grass, and rarely also of leaves.
   [1913 Webster]