The Collaborative International Dictionary of English v.0.48:

Trencher \Trench"er\, n. [OE. trencheoir, F. tranchoir, fr.
   trancher to cut, carve. See Trench, v. t.]
   1. One who trenches; esp., one who cuts or digs ditches.
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   2. A large wooden plate or platter, as for table use.
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   3. The table; hence, the pleasures of the table; food.
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            It could be no ordinary declension of nature that
            could bring some men, after an ingenuous education,
            to place their "summum bonum" upon their trenchers.
                                                  --South.
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   Trencher cap, the cap worn by studens at Oxford and
      Cambridge Universities, having a stiff, flat, square
      appendage at top. A similar cap used in the United States
      is called Oxford cap, mortar board, etc.

   Trencher fly, a person who haunts the tables of others; a
      parasite. [R.] --L'Estrange.

   Trencher friend, one who frequents the tables of others; a
      sponger.

   Trencher mate, a table companion; a parasite; a trencher
      fly. --Hooker.
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WordNet (r) 3.0 (2006):

trencher
    n 1: someone who digs trenches
    2: a wooden board or platter on which food is served or carved