The Collaborative International Dictionary of English v.0.48:

Sturdy \Stur"dy\, n. [OF. estourdi giddiness, stupefaction.]
   (Vet.)
   A disease in sheep and cattle, marked by great nervousness,
   or by dullness and stupor.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Sturdy \Stur"dy\, a. [Compar. Sturdier; superl. Sturdiest.]
   [OE. sturdi inconsiderable, OF. estourdi stunned, giddy,
   thoughtless, rash, F. ['e]tourdi, p. p. of OF. estourdir to
   stun, to render giddy, to amaze, F. ['e]tourdir; of uncertain
   origin. The sense has probably been influenced by E. stout.]
   1. Foolishly obstinate or resolute; stubborn; unrelenting;
      unfeeling; stern.
      [1913 Webster]

            This sturdy marquis gan his hearte dress
            To rue upon her wifely steadfastness. --Chaucer.
      [1913 Webster]

            This must be done, and I would fain see
            Mortal so sturdy as to gainsay.       --Hudibras.
      [1913 Webster]

            A sturdy, hardened sinner shall advance to the
            utmost pitch of impiety with less reluctance than he
            took the first steps.                 --Atterbury.
      [1913 Webster]

   2. Resolute, in a good sense; or firm, unyielding quality;
      as, a man of sturdy piety or patriotism.
      [1913 Webster]

   3. Characterized by physical strength or force; strong;
      lusty; violent; as, a sturdy lout.
      [1913 Webster]

            How bowed the woods beneath their sturdy stroke!
                                                  --Gray.
      [1913 Webster]

   4. Stiff; stout; strong; as, a sturdy oak. --Milton.
      [1913 Webster]

            He was not of any delicate contexture; his limbs
            rather sturdy than dainty.            --Sir H.
                                                  Wotton.
      [1913 Webster]

   Syn: Hardy; stout; strong; firm; robust; stiff.
        [1913 Webster]

WordNet (r) 3.0 (2006):

sturdy
    adj 1: having rugged physical strength; inured to fatigue or
           hardships; "hardy explorers of northern Canada"; "proud
           of her tall stalwart son"; "stout seamen"; "sturdy young
           athletes" [syn: hardy, stalwart, stout, sturdy]
    2: not making concessions; "took an uncompromising stance in the
       peace talks"; "uncompromising honesty" [syn:
       uncompromising, sturdy, inflexible] [ant:
       compromising, conciliatory, flexible]
    3: substantially made or constructed; "sturdy steel shelves";
       "sturdy canvas"; "a tough all-weather fabric"; "some plastics
       are as tough as metal" [syn: sturdy, tough]

Moby Thesaurus II by Grady Ward, 1.0:

83 Moby Thesaurus words for "sturdy":
   adamantine, athletic, beefy, bouncing, brawny, bulky, burly, dense,
   determined, doughty, durable, enduring, firm, firm as Gibraltar,
   flush, forceful, forcible, forcy, full-blooded, full-strength,
   gutsy, gutty, hale, hale and hearty, hard, hard as nails, hardy,
   hearty, heavy, hefty, husky, indomitable, infrangible, iron-hard,
   lasting, lusty, made of iron, massive, mighty, muscular, nervy,
   obstinate, potent, powerful, puissant, red-blooded, resolute,
   rigid, robust, robustious, robustuous, rude, rugged, solid, sound,
   stable, stalwart, staunch, steadfast, steady, steely, stout,
   strapping, strong, strong as brandy, strong as strong,
   strong-willed, substantial, tenacious, tough, unbreakable,
   uncompromising, unfaltering, unswerving, unwavering, unyielding,
   vigorous, vital, well-built, well-constructed, well-founded,
   well-grounded, well-made