1. spearlike, as weapons.
2. shaped like the head of a spear.
3. (of a leaf) triangular, with two spreading lobes at the base.
Etymology: late 1700s, from Latin hasta, spear.
Primarily used in botany (to describe leaves); also used in biology to describe the features of some insects, crustaceans, etc.
Plants with hastate leaves include Convolvulus arvensis (field bindweed), Polygonum arifolium (tearthumb), HIbiscus militaris (halberdleaf rosemallow), Atriplex calotheca (hastate orache), and Rumex acetocella (common sheep sorrel).
Wikipedia has a long list of terms for different leaf shapes.
A 1903 patent for a type of hook-and-eye closure (from Peter M. Kling) says "In a hook-and-eye fastening device, an eye member of hastate formation and a hook member comprising an eyeleted shank, a hastate bill, a loop formed by the converging of the wires behind the hastate bill and the arms of the shank diverging from the loop to form a guideway for the reception of the engaging end of the eye member". They don't write patents like they used to.