The Collaborative International Dictionary of English v.0.48:

caballero \ca`bal*le"ro\, n. [Sp. Cf. Cavalier.]
   A knight or cavalier; hence, a gentleman.
   [Webster 1913 Suppl.]

Moby Thesaurus II by Grady Ward, 1.0:

70 Moby Thesaurus words for "caballero":
   Bayard, Casanova, Don Juan, Don Quixote, Gawain, Lancelot,
   Lothario, Ritter, Romeo, Sidney, Sir Galahad, amoroso, bachelor,
   banneret, baronet, beau, boyfriend, broncobuster, buckaroo,
   cavalier, cavaliere servente, cavalryman, chevalier, circus rider,
   companion, cowboy, cowgirl, cowpuncher, equestrian, equestrienne,
   esquire, fellow, flame, gallant, gaucho, gigolo, horse soldier,
   horseback rider, horsebacker, horseman, horsewoman, inamorato,
   jockey, knight, knight bachelor, knight banneret, knight baronet,
   knight-errant, lady-killer, love-maker, man, mounted policeman,
   necker, old man, petter, philanderer, postboy, postilion, puncher,
   rider, roughrider, seducer, sheik, squire, steeplechaser,
   sugar daddy, swain, trick rider, vaquero, young man