The Collaborative International Dictionary of English v.0.48:

Cippus \Cip"pus\, n.; pl. Cippi. [L., stake, post.]
   A small, low pillar, square or round, commonly having an
   inscription, used by the ancients for various purposes, as
   for indicating the distances of places, for a landmark, for
   sepulchral inscriptions, etc. --Gwilt.
   [1913 Webster]