From Hidden Frontier

The Cardassian rank system is based on three ranks (Legate, Gul, Glinn, Kara and Gil). It is assumed that while Cardassians may hold the same rank, it is the nature of their duties that defines their military hierarchy (e.g., Prefect of a territory, Commander of a Cardassian Order, etc.).

The Star Trek: Deep Space Nine Technical Manual lists another Cardassian rank below glinn, "gil," presumably a low officer grade or noncom rank.

References

• Cardassian Ranks article at Memory Alpha