The Collaborative International Dictionary of English v.0.48:

Shelter \Shel"ter\, v. i.
   To take shelter.
   [1913 Webster]

         There oft the Indian herdsman, shunning heat,
         Shelters in cool.                        --Milton.
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The Collaborative International Dictionary of English v.0.48:

Shelter \Shel"ter\, n. [Cf. OE. scheltrun, shiltroun,
   schelltrome, scheldtrome, a guard, squadron, AS. scildtruma a
   troop of men with shields; scild shield + truma a band of
   men. See Shield, n.]
   1. That which covers or defends from injury or annoyance; a
      protection; a screen.
      [1913 Webster]

            The sick and weak the healing plant shall aid,
            From storms a shelter, and from heat a shade.
                                                  --Pope.
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   2. One who protects; a guardian; a defender.
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            Thou [God] hast been a shelter for me. --Ps. lxi. 3.
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   3. The state of being covered and protected; protection;
      security.
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            Who into shelter takes their tender bloom. --Young.
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   Shelter tent,a small tent made of pieces of cotton duck
      arranged to button together. In field service the soldiers
      carry the pieces.
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   Syn: Asylum; refuge; retreat; covert; sanctuary; protection;
        defense; security.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Shelter \Shel"ter\, v. t. [imp. & p. p. Sheltered; p. pr. &
   vb. n. Sheltering.]
   1. To be a shelter for; to provide with a shelter; to cover
      from injury or annoyance; to shield; to protect.
      [1913 Webster]

            Those ruins sheltered once his sacred head.
                                                  --Dryden.
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            You have no convents . . . in which such persons may
            be received and sheltered.            --Southey.
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   2. To screen or cover from notice; to disguise.
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            In vain I strove to cheek my growing flame,
            Or shelter passion under friendship's name. --Prior.
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   3. To betake to cover, or to a safe place; -- used
      reflexively.
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            They sheltered themselves under a rock. --Abp.
                                                  Abbot.
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WordNet (r) 3.0 (2006):

shelter
    n 1: a structure that provides privacy and protection from
         danger
    2: protective covering that provides protection from the weather
    3: the condition of being protected; "they were huddled together
       for protection"; "he enjoyed a sense of peace and protection
       in his new home" [syn: protection, shelter]
    4: a way of organizing business to reduce the taxes it must pay
       on current earnings [syn: tax shelter, shelter]
    5: temporary housing for homeless or displaced persons
    v 1: provide shelter for; "After the earthquake, the government
         could not provide shelter for the thousands of homeless
         people"
    2: invest (money) so that it is not taxable

Moby Thesaurus II by Grady Ward, 1.0:

128 Moby Thesaurus words for "shelter":
   abri, accommodation, accommodations, air-raid shelter, arm, armor,
   asylum, bed, berth, billet, blanket, bless, bomb shelter,
   bombproof, bunk, bunker, cave, chamber, champion, cloak, coat,
   compass about, concealment, copyright, cover, coverage, covering,
   covert, coverture, cowl, cowling, curtain, cushion, cyclone cellar,
   defend, defense, den, diggings, digs, domicile, domiciliate, drape,
   drapery, dugout, dwelling, earth, ensure, eye, fallout shelter,
   fence, fend, foxhole, funk hole, guarantee, guard, guise,
   habitation, hanging, harbor, harborage, haven, hermitage, hide,
   hideaway, hideout, hole up, home, hood, house, housing, insure,
   keep, keep from harm, lay low, lee, lie low, living quarters,
   lodge, lodging, lodgings, lodgment, make safe, mantle, mask,
   nestle, pall, patent, police, port, preservation, protect,
   protection, protective custody, put up, quarter, quarters, refuge,
   register, retirement, retreat, ride shotgun for, roof, room, rooms,
   roost, safeguard, safekeeping, safety, safety zone, sanctuary,
   screen, secure, security, shade, shadow, shield, shroud,
   sleeping place, stable, storm cave, storm cellar, tower, trench,
   umbrella, underwrite, veil, vestment, watchful eye