The Collaborative International Dictionary of English v.0.48:

Vail \Vail\, v. t. [Aphetic form of avale. See Avale, Vale.]
   [Written also vale, and veil.]
   1. To let fall; to allow or cause to sink. [Obs.]
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            Vail your regard
            Upon a wronged, I would fain have said, a maid!
                                                  --Shak.
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   2. To lower, or take off, in token of inferiority, reverence,
      submission, or the like.
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            France must vail her lofty-plumed crest! --Shak.
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            Without vailing his bonnet or testifying any
            reverence for the alleged sanctity of the relic.
                                                  --Sir. W.
                                                  Scott.
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The Collaborative International Dictionary of English v.0.48:

Vail \Vail\ (v[=a]l), v. i.
   To yield or recede; to give place; to show respect by
   yielding, uncovering, or the like. [Written also vale, and
   veil.] [Obs.]
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         Thy convenience must vail to thy neighbor's necessity.
                                                  --South.
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The Collaborative International Dictionary of English v.0.48:

Veil \Veil\, v. t. [imp. & p. p. Veiled; p. pr. & vb. n.
   Veiling.] [Cf. OF. veler, F. voiler, L. velarc. See Veil,
   n.] [Written also vail.]
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   1. To throw a veil over; to cover with a veil.
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            Her face was veiled; yet to my fancied sight,
            Love, sweetness, goodness, in her person shined.
                                                  --Milton.
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   2. Fig.: To invest; to cover; to hide; to conceal.
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            To keep your great pretenses veiled.  --Shak.
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The Collaborative International Dictionary of English v.0.48:

Veil \Veil\ (v[=a]l), n. [OE. veile, OF. veile, F. voile, L.
   velum a sail, covering, curtain, veil, probably fr. vehere to
   bear, carry, and thus originally, that which bears the ship
   on. See Vehicle, and cf. Reveal.] [Written also vail.]
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   1. Something hung up, or spread out, to intercept the view,
      and hide an object; a cover; a curtain; esp., a screen,
      usually of gauze, crape, or similar diaphnous material, to
      hide or protect the face.
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            The veil of the temple was rent in twain. --Matt.
                                                  xxvii. 51.
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            She, as a veil down to the slender waist,
            Her unadorn['e]d golden tresses wore. --Milton.
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   2. A cover; a disguise; a mask; a pretense.
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            [I will] pluck the borrowed veil of modesty from the
            so seeming Mistress Page.             --Shak.
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   3. (Bot.)
      (a) The calyptra of mosses.
      (b) A membrane connecting the margin of the pileus of a
          mushroom with the stalk; -- called also velum.
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   4. (Eccl.) A covering for a person or thing; as, a nun's
      veil; a paten veil; an altar veil.
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   5. (Zool.) Same as Velum, 3.
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   To take the veil (Eccl.), to receive or be covered with, a
      veil, as a nun, in token of retirement from the world; to
      become a nun.
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The Collaborative International Dictionary of English v.0.48:

Caul \Caul\ (k[add]l), n. [OE. calle, kelle, prob. fr. F. cale;
   cf. Ir. calla a veil.]
   1. A covering of network for the head, worn by women; also, a
      net. --Spenser.
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   2. (Anat.) The fold of membrane loaded with fat, which covers
      more or less of the intestines in mammals; the great
      omentum. See Omentum.
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            The caul serves for the warming of the lower belly.
                                                  --Ray.
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   3. A part of the amnion, one of the membranes enveloping the
      fetus, which sometimes is round the head of a child at its
      birth; -- called also a veil.
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            It is deemed lucky to be with a caul or membrane
            over the face. This caul is esteemed an infallible
            preservative against drowning . . . According to
            Chrysostom, the midwives frequently sold it for
            magic uses.                           --Grose.
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            I was born with a caul, which was advertised for
            sale, in the newspapers, at the low price of fifteen
            guineas.                              --Dickens.
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WordNet (r) 3.0 (2006):

veil
    n 1: a garment that covers the head and face [syn: head
         covering, veil]
    2: a membranous covering attached to the immature fruiting body
       of certain mushrooms [syn: veil, velum]
    3: the inner membrane of embryos in higher vertebrates
       (especially when covering the head at birth) [syn: caul,
       veil, embryonic membrane]
    4: a vestment worn by a priest at High Mass in the Roman
       Catholic Church; a silk shawl [syn: humeral veil, veil]
    v 1: to obscure, or conceal with or as if with a veil; "women in
         Afghanistan veil their faces" [ant: unveil]
    2: make undecipherable or imperceptible by obscuring or
       concealing; "a hidden message"; "a veiled threat" [syn:
       obscure, blot out, obliterate, veil, hide]