a swaggering braggart or boaster
About the Word:
The Cacafuego was a Spanish ship captured in 1579 by the English admiral Sir Francis Drake.
The word may have developed its insulting sense because some sailors either the ones who lost the ship or the ones who won it did some serious bragging.
Cacafuego, by the way, comes from the Spanish word fuego, meaning "fire," and, ultimately, the Latin cacare, meaning (ahem) "to void as excrement." The word probably referred to the ship's cannon fire.