tri·er·arch 
(trīə-rärk′)
(trīə-rärk′)n.
1. The captain of a Greek trireme.
2. An Athenian who outfitted and maintained a trireme as a part of his civic duties.
[Latin triērarchus, from Greek triērarkhos : triērēs, trireme; see trei- in the Appendix of Indo-European roots + arkhos, ruler; see -ARCH.]