Noun
(bullfighting) Any of the three stages of a bullfight: the vara, the banderilla and finally the death.
(military) A mutually supportive infantry formation made up of pikemen, swordsmen and arquebusiers or musketeers.
Source: en.wiktionary.orgI am proud to place Tercio Red River into a conservation easement forever protecting this spectacular landscape with Colorado Open Lands. Louis Bacon
In 1640, a tercio of a thousand musket armed dragons was established in Spain itself. Source: Internet
The Spanish tercio and later formations relegated cavalry to a supporting role. Source: Internet