noun, masculineplural: triarios
triarius
“De estos, quatrocientos eran astados, novecientos príncipes, novecientos triarios, ó lo que es lo mismo, dos mil doscientos de tropa de linea, ademas de doscientos astados y novecientos rorarios armados á la ligera, […]” — Of these, four hundred were hastati, nine hundred princes, nine hundred triarii, or equivalent, two-thousand two hundred line troops, as well as two hundred hastati and nine hundred lightly armed rorarios […]
Borrowed from Latin triārius.