The Collaborative International Dictionary of English v.0.48:

Sty \Sty\ (st[imac]), n.; pl. Sties (st[imac]z). [Written also
   stigh.] [AS. stigu, fr. st[imac]gan to rise; originally,
   probably, a place into which animals climbed or went up.
   [root]164. See Sty, v. i., and cf. Steward.]
   1. A pen or inclosure for swine.
      [1913 Webster]

   2. A place of bestial debauchery.
      [1913 Webster]

            To roll with pleasure in a sensual sty. --Milton.
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The Collaborative International Dictionary of English v.0.48:

Sty \Sty\, v. t. [imp. & p. p. Stied (st[imac]d); p. pr. & vb.
   n. Stying (st[imac]"[i^]ng).]
   To shut up in, or as in, a sty. --Shak.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Sty \Sty\, v. i. [OE. stien, sti[yogh]en, AS. st[imac]gan to
   rise; akin to D. stijgen, OS. & OHG. st[imac]gan, G. steigen,
   Icel. st[imac]ga, Sw. stiga, Dan. stige, Goth. steigan, L.
   vestigium footstep, Gr. ? to walk, to go, Skr. stigh to
   mount. Cf. Distich, Stair steps, Stirrup, Sty a boil,
   a pen for swine, Vestige.]
   To soar; to ascend; to mount. See Stirrup. [Obs.]
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         With bolder wing shall dare aloft to sty,
         To the last praises of this Faery Queene. --Spenser.
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The Collaborative International Dictionary of English v.0.48:

Sty \Sty\, n. [For older styan, styanye, understood as sty on
   eye, AS. st[imac]gend (sc. e['a]ge eye), properly, rising, or
   swelling (eye), p. p. of st[imac]gan to rise. See Sty, v.
   i.] (Med.)
   An inflamed swelling or boil on the edge of the eyelid.
   [Written also stye.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

sty
    n 1: an infection of the sebaceous gland of the eyelid [syn:
         sty, stye, hordeolum, eye infection]
    2: a pen for swine [syn: sty, pigsty, pigpen]

Moby Thesaurus II by Grady Ward, 1.0:

143 Moby Thesaurus words for "sty":
   Augean stables, Sodom, abscess, amaurosis, aposteme, bed sore,
   birthmark, blackhead, blain, bleb, blemish, blepharitis, blister,
   boil, bubo, bulla, bunion, canker, canker sore, carbuncle,
   cataract, cesspit, cesspool, chancre, chancroid, check, chilblain,
   choroiditis, cicatrix, cold sore, comedo, conjunctivitis, crack,
   crater, craze, cross-eye, defacement, defect, defective vision,
   deformation, deformity, den, detached retina, disfiguration,
   disfigurement, distortion, dump, eschar, esotropia, eye defect,
   fault, felon, fester, festering, fever blister, fistula, flaw,
   freckle, furuncle, furunculus, gathering, glaucoma, gumboil,
   gutta serena, hemangioma, hemorrhoids, hickey, hole, hovel, iritis,
   keloid, keratitis, kibe, kink, lentigo, lesion, milium, mole,
   needle scar, nevus, optic neuritis, pandemonium, papula, papule,
   paronychia, parulis, pesthole, petechia, pigpen, pigsty, piles,
   pimple, pink eye, pit, plague spot, pock, pockmark, polyp,
   port-wine mark, port-wine stain, pustule, retinoblastoma, rift,
   rising, rookery, scab, scar, scratch, sebaceous cyst, slum,
   soft chancre, sore, split, stable, stigma, strawberry mark,
   suppuration, swelling, tenement, the slums, trachoma, track,
   tubercle, tumbledown shack, twist, ulcer, ulceration, uveitis,
   verruca, vesicle, wale, walleye, warp, warren, wart, weal, welt,
   wen, wheal, whelk, whitehead, whitlow, wound