The Collaborative International Dictionary of English v.0.48:

Hackly \Hac"kly\ (h[a^]k"l[y^]), a. [From Hackle.]
   1. Rough or broken, as if hacked.
      [1913 Webster]

   2. (Min.) Having fine, short, and sharp points on the
      surface; as, the hackly fracture of metallic iron.
      [1913 Webster]