The Collaborative International Dictionary of English v.0.48:

Sabellian \Sa*bel"li*an\, a.
   Pertaining to the doctrines or tenets of Sabellius. See
   Sabellian, n.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Sabellian \Sa*bel"li*an\, n. (Eccl. Hist.)
   A follower of Sabellius, a presbyter of Ptolemais in the
   third century, who maintained that there is but one person in
   the Godhead, and that the Son and Holy Spirit are only
   different powers, operations, or offices of the one God the
   Father.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Sabellian
    n 1: an extinct Osco-Umbrian language of ancient Italy that
         survives only in a few inscriptions