The Collaborative International Dictionary of English v.0.48:

Mellow \Mel"low\, v. t. [imp. & p. p. Mellowed; p. pr. & vb.
   n. Mellowing.]
   To make mellow. --Shak.
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         If the Weather prove frosty to mellow it [the ground],
         they do not plow it again till April.    --Mortimer.
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         The fervor of early feeling is tempered and mellowed by
         the ripeness of age.                     --J. C.
                                                  Shairp.
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The Collaborative International Dictionary of English v.0.48:

Mellow \Mel"low\, a. [Compar. Mellower; superl. Mellowest.]
   [OE. melwe; cf. AS. mearu soft, D. murw, Prov. G. mollig
   soft, D. malsch, and E. meal flour.]
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   1. Soft or tender by reason of ripeness; having a tender
      pulp; as, a mellow apple.
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   2. Hence:
      (a) Easily worked or penetrated; not hard or rigid; as, a
          mellow soil. "Mellow glebe." --Drayton
      (b) Not coarse, rough, or harsh; subdued; soft; rich;
          delicate; -- said of sound, color, flavor, style, etc.
          "The mellow horn." --Wordsworth. "The mellow-tasted
          Burgundy." --Thomson.
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                The tender flush whose mellow stain imbues
                Heaven with all freaks of light.  --Percival.
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   3. Well matured; softened by years; genial; jovial.
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            May health return to mellow age.      --Wordsworth.
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            As merry and mellow an old bachelor as ever followed
            a hound.                              --W. Irving.
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   4. Warmed by liquor; slightly intoxicated. --Addison.
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The Collaborative International Dictionary of English v.0.48:

Mellow \Mel"low\, v. i.
   To become mellow; as, ripe fruit soon mellows. "Prosperity
   begins to mellow." --Shak.
   [1913 Webster]

WordNet (r) 3.0 (2006):

mellow
    adv 1: (obsolete) in a mellow manner [syn: mellowly, mellow]
    adj 1: unhurried and relaxed; "a mellow conversation" [syn:
           laid-back, mellow]
    2: having a full and pleasing flavor through proper aging; "a
       mellow port"; "mellowed fruit" [syn: mellow, mellowed]
    3: having attained to kindliness or gentleness through age and
       experience; "mellow wisdom"; "the peace of mellow age" [syn:
       mellow, mellowed]
    4: having attained to kindliness or gentleness through age and
       experience; "mellow wisdom"; "the peace of mellow age"
    5: slightly and pleasantly intoxicated from alcohol or a drug
       (especially marijuana) [syn: high, mellow]
    v 1: soften, make mellow; "Age and experience mellowed him over
         the years"
    2: become more relaxed, easygoing, or genial; "With age, he
       mellowed" [syn: mellow, melt, mellow out]
    3: make or grow (more) mellow; "These apples need to mellow a
       bit more"; "The sun mellowed the fruit"