The Collaborative International Dictionary of English v.0.48:

Herodian \He*ro"di*an\ (h[-e]*r[=o]"d[i^]*an), prop. n. (Jewish
   Hist.)
   One of a party among the Jews, composed of partisans of Herod
   of Galilee. They joined with the Pharisees against Christ.
   [1913 Webster]