According to Father Sibyla, “The word filibustero […] means a dangerous patriot who will soon be on the gallows, or else a conceited fellow” (15). The actual etymology of the word dates it to the 16th century, and it most likely derives from the Dutch vrijbueter (freebooter) and the French flibustier. Hispanicized, the word became filibustero. Regardless of its origin, each word once described a person engaging in unauthorized warfare against a foreign country. This meaning has become dated in both Dutch and French; the English filibuster also has a different meaning (using prolonged speech to obstruct progress within a legislative assembly). Nevertheless, Father Sibyla’s definition and other definitions describe the motives of many of the novel’s characters.

Simoun/Ibarra mostly connotes the original meaning of filibustero: He wants to wage war against the clergy and Spanish government who abused him and his loved ones (his father and María Clara), but also the Filipino populace. He and Cabesang Tales are filibusteros in their acts of vengeance. Basilio, Isagani, and other students are filibusteros as per Father Sibyla’s definition. The clergy and government view them as such because they seek social reform through education; the students want to upset the status quo that the clergy wishes to maintain.