The term 'fortis vir' translates to 'brave man' in Latin and serves as an example of how third declension adjectives function in the language. In this case, 'fortis' is a third declension adjective meaning 'brave' or 'strong,' and 'vir' is a masculine noun meaning 'man.' This combination highlights how adjectives agree with the nouns they modify in gender, number, and case, showcasing an essential aspect of Latin grammar.