A warrior is a soldier who lives for combat.
The warrior ethos had been an important aspect of Klingon society since the time of Kahless, but the warrior aspects became much more dominant beginning in the early 22nd century. Previously, Klingon society was regarded as socially balanced, but over time the warrior caste gained greater prominence, to the point where the Klingons widely came to be regarded as a "warrior race." (ENT: "Broken Bow", "Judgment") The Klingon Bird-of-Prey of the mid-24th century was said to be equipped with the Klingon Empire's "best weapons" and "finest warriors." (TNG: "A Matter Of Honor")
In 2368, Lieutenant Worf said in his personal log that he would "rather fight ten Balduk warriors than face one small child" after he found out his son, Alexander, was coming aboard the Enterprise. (TNG: "New Ground")
Although term is not always, entirely universal, these races are mostly warriors.