GNU Collaborative International Dictionary of English

Found 2 definitions

1.       
   Tetrarch , n. [L. tetrarches, Gr. , ; τέτρα- (see Tetra-) +  a ruler,  to lead; rule: cf. F. tétrarque. See Arch, a.] (Rom. Antiq.) A Roman governor of the fourth part of a province; hence, any subordinate or dependent prince; also, a petty king or sovereign.
   1913 Webster
         
       

2.       
   Tetrarch, a. Four. [Obs.]
   Fuller.
   
   1913 Webster