This means combative or belligerent. Here are some sentences. He has a pugnacious nature, and always ends up in a fight. Her dog is pugnacious, and I'm afraid he'll bite me. A pugnacious attitude...
I've never heard of the word, "pugnacious."
The young student's "quick to fight" nature was described as overly pugnacious to the school's principal by the child's teacher .