n.1 Rom.Hist. a the governor of a fourth part of a country or province. b a subordinate ruler.
2 one of four joint rulers.
Derivatives:
tetrarchate n. tetrarchical adj. tetrarchy n. (pl. -ies).
Etymology: ME f. LL tetrarcha f. L tetrarches f. Gk tetrarkhes (as TETRA-, arkho rule)