triarian means occupying the third post or rank. Lexicurio rates it Sui generis — a strength score of 87 out of 100.
Etymology
Latin triarii (plural), a class of Roman soldiers who formed the third rank from the front, from tres, tria (“three”).
adj
- Occupying the third post or rank.“Let the brave Second and Triarian Band
Firm against all Impression stand”
noun
- A soldier of the triarii