The Collaborative International Dictionary of English v.0.48:

Spartan \Spar"tan\, a. [L. Spartanus.]
   Of or pertaining to Sparta, especially to ancient Sparta;
   hence, hardy; undaunted; as, Spartan souls; Spartan bravey.
   -- n. A native or inhabitant of Sparta; figuratively, a
   person of great courage and fortitude.
   [1913 Webster]
   [1913 Webster]

WordNet (r) 3.0 (2006):

Spartan
    adj 1: of or relating to or characteristic of Sparta or its
           people
    2: resolute in the face of pain or danger or adversity; "spartan
       courage"
    3: unsparing and uncompromising in discipline or judgment; "a
       parent severe to the pitch of hostility"- H.G.Wells; "a hefty
       six-footer with a rather severe mien"; "a strict
       disciplinarian"; "a Spartan upbringing" [syn: severe,
       spartan]
    4: practicing great self-denial; "Be systematically
       ascetic...do...something for no other reason than that you
       would rather not do it"- William James; "a desert nomad's
       austere life"; "a spartan diet"; "a spartan existence" [syn:
       ascetic, ascetical, austere, spartan]
    n 1: a resident of Sparta

Moby Thesaurus II by Grady Ward, 1.0:

182 Moby Thesaurus words for "Spartan":
   Apostolic, Encratic, Laconian, Lenten, Pythagorean, Rechabite,
   Shaker, Spartanic, Stoic, abbreviated, abridged, abstemious,
   abstinent, accepting, aposiopestic, armed with patience, ascetic,
   astringent, austere, authoritarian, bald, bare, brief, brusque,
   candid, celibate, chaste, clam, clipped, close, common,
   commonplace, compact, compendious, compressed, concise, condensed,
   continent, contracted, controlled, crisp, curt, cut, demanding,
   direct, disciplined, docked, dour, dry, dull, dwarfed, dwarfish,
   elliptic, endurant, enduring, epigrammatic, exacting, exigent,
   exiguous, forbearing, frank, frugal, fruitarian, gnomic, grim,
   hard, harsh, homely, homespun, impoverished, indulgent, inornate,
   jejune, laconic, lean, lenient, limited, long-suffering,
   longanimous, man of iron, matter-of-fact, meager, mean, meticulous,
   miserly, narrow, natural, neat, nephalistic, niggardly,
   on the wagon, open, paltry, parsimonious, patient, patient as Job,
   persevering, philosophical, pithy, plain, plain-speaking,
   plain-spoken, pointed, poor, prosaic, prosing, prosy, pruned, puny,
   pure, reserved, rigid, rigorous, rugged, rustic, scant, scanty,
   scrawny, scrimp, scrimpy, self-controlled, self-denying,
   sententious, severe, sexually abstinent, short, short and sweet,
   shortened, simple, simple-speaking, skimp, skimpy, slender, slight,
   slim, small, sober, spare, sparing, stark, starvation, stern,
   stingy, stinted, stoic, straightforward, straitened, strict,
   stringent, stunted, subsistence, succinct, summary, sworn off,
   synopsized, taciturn, teetotal, terse, thin, tight, to the point,
   tolerant, tolerating, tolerative, tough, truncated, unadorned,
   unaffected, understanding, unelaborate, unfancy, unfussy,
   unimaginative, unnourishing, unnutritious, unornate, unpoetical,
   unsparing, unvarnished, vegetarian, watered, watery