The Collaborative International Dictionary of English v.0.48:

Shelter \Shel"ter\, v. i.
   To take shelter.
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         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.
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            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.
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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.
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            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