What is "arrowheaded characters"

Arrowheaded \Ar"row*head`ed\, a. Shaped like the head of an arrow; cuneiform.

Arrowheaded characters, characters the elements of which consist of strokes resembling arrowheads, nailheads, or wedges; -- hence called also nail-headed, wedge-formed, cuneiform, or cuneatic characters; the oldest written characters used in the country about the Tigris and Euphrates, and subsequently in Persia, and abounding among the ruins of Persepolis, Nineveh, and Babylon. See Cuneiform.