The Collaborative International Dictionary of English v.0.48:

Prowess \Prow"ess\, n. [OF. proece, proesce, F. prouesse. See
   Prow, a.]
   Distinguished bravery; valor; especially, military bravery
   and skill; gallantry; intrepidity; fearlessness. --Chaucer.
   Sir P. Sidney.
   [1913 Webster]

         He by his prowess conquered all France.  --Shak.
   [1913 Webster]

WordNet (r) 3.0 (2006):

prowess
    n 1: a superior skill that you can learn by study and practice
         and observation; "the art of conversation"; "it's quite an
         art" [syn: art, artistry, prowess]

Moby Thesaurus II by Grady Ward, 1.0:

106 Moby Thesaurus words for "prowess":
   Dutch courage, ability, address, adeptness, adroitness, airmanship,
   aptitude, artfulness, artisanship, artistry, boldness, braveness,
   bravery, bravura, brilliance, capability, capacity, chivalrousness,
   chivalry, cleverness, command, competence, conspicuous gallantry,
   control, coordination, courage, courageousness, craft,
   craftsmanship, cunning, daring, dauntlessness, deftness, dexterity,
   dexterousness, dextrousness, diplomacy, doughtiness, efficiency,
   expertise, facility, fearlessness, finesse, fortitude, gallantness,
   gallantry, gallantry under fire, genius, grace, greatheartedness,
   grip, handiness, heroicalness, heroism, horsemanship,
   ingeniousness, ingenuity, intrepidity, intrepidness, knightliness,
   know-how, lionheartedness, manfulness, manhood, manliness,
   marksmanship, martial spirit, mastership, mastery, mettle,
   military spirit, pot-valor, practical ability, proficiency,
   quickness, readiness, resource, resourcefulness, savoir-faire,
   savvy, seamanship, skill, skillfulness, sleight, soldierly quality,
   stalwartness, stoutheartedness, stoutness, style, tact,
   tactfulness, talent, technical brilliance, technical mastery,
   technical skill, technique, timing, valiance, valiancy, valor,
   valorousness, virtue, virtuosity, wit, wizardry, workmanship