The Collaborative International Dictionary of English v.0.48:

Slate \Slate\ (sl[=a]t), n. [OE. slat, sclat, OF. esclat a
   shiver, splinter, F. ['e]clat, fr. OF. esclater to shiver, to
   chip, F. ['e]clater, fr. OHG. sleizen to tear, slit, split,
   fr. sl[imac]zan to slit, G. schleissen. See Slit, v. t.,
   and cf. Eclat.]
   1. (Min.) An argillaceous rock which readily splits into thin
      plates; argillite; argillaceous schist.
      [1913 Webster]

   2. Any rock or stone having a slaty structure.
      [1913 Webster]

   3. A prepared piece of such stone. Especially:
      (a) A thin, flat piece, for roofing or covering houses,
          etc.
      (b) A tablet for writing upon.
          [1913 Webster]

   4. An artificial material, resembling slate, and used for the
      above purposes.
      [1913 Webster]

   5. A thin plate of any material; a flake. [Obs.]
      [1913 Webster]

   6. (Politics) A list of candidates, prepared for nomination
      or for election; a list of candidates, or a programme of
      action, devised beforehand. [Cant, U.S.] --Bartlett.
      [1913 Webster]

   Adhesive slate (Min.), a kind of slate of a greenish gray
      color, which absorbs water rapidly, and adheres to the
      tongue; whence the name.

   Aluminous slate, or Alum slate (Min.), a kind of slate
      containing sulphate of alumina, -- used in the manufacture
      of alum.

   Bituminous slate (Min.), a soft species of sectile clay
      slate, impregnated with bitumen.

   Hornblende slate (Min.), a slaty rock, consisting
      essentially of hornblende and feldspar, useful for
      flagging on account of its toughness.

   Slate ax or Slate axe, a mattock with an ax end, used in
      shaping slates for roofs, and making holes in them for the
      nails.

   Slate clay (Geol.), an indurated clay, forming one of the
      alternating beds of the coal measures, consisting of an
      infusible compound of alumina and silica, and often used
      for making fire bricks. --Tomlinson.

   Slate globe, a globe the surface of which is made of an
      artificial slatelike material.

   Slate pencil, a pencil of slate, or of soapstone, used for
      writing on a slate.

   Slate rocks (Min.), rocks which split into thin laminae,
      not necessarily parallel to the stratification; foliated
      rocks.

   Slate spar (Min.), a variety of calcite of silvery white
      luster and of a slaty structure.

   Transparent slate, a plate of translucent material, as
      ground glass, upon which a copy of a picture, placed
      beneath it, can be made by tracing.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Slate \Slate\, v. t. [imp. & p. p. Slated; p. pr. & vb. n.
   Slating.]
   1. To cover with slate, or with a substance resembling slate;
      as, to slate a roof; to slate a globe.
      [1913 Webster]

   2. To register (as on a slate and subject to revision), for
      an appointment. [Polit. Cant]
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Slate \Slate\, v. t. [Cf. AS. sl[=ae]ting a privilege of
   hunting.]
   To set a dog upon; to bait; to slat. See 2d Slat, 3. [Prov.
   Eng. & Scot.] [Written also slete.] --Ray.
   [1913 Webster]

WordNet (r) 3.0 (2006):

slate
    n 1: (formerly) a writing tablet made of slate
    2: thin layers of rock used for roofing [syn: slate,
       slating]
    3: a fine-grained metamorphic rock that can be split into thin
       layers
    4: a list of candidates nominated by a political party to run
       for election to public offices [syn: slate, ticket]
    v 1: designate or schedule; "He slated his talk for 9 AM"; "She
         was slated to be his successor"
    2: enter on a list or slate for an election; "He was slated for
       borough president"
    3: cover with slate; "slate the roof"

Moby Thesaurus II by Grady Ward, 1.0:

70 Moby Thesaurus words for "slate":
   Australian ballot, Indiana ballot, Massachusetts ballot,
   absentee ballot, agenda, ballot, batting order, bill, bill of fare,
   blanket ballot, blister, blueprint, board, book, brick, budget,
   calendar, card, carte du jour, castigate, clapboard, crawl, docket,
   excoriate, face, glass, glaze, lambaste, lath, line up, lineup,
   list of agenda, long ballot, menu, nonpartisan ballot,
   office-block ballot, paper, party emblem, party-column ballot,
   plank, playbill, program, program of operation, programma,
   prospectus, protocol, proxy, revet, roster, sample ballot, scarify,
   scathe, schedule, score, scourge, shake, sheathe, shingle,
   short ballot, split ticket, stone, straight ticket, thatch, ticket,
   tile, veneer, wall in, wall up, wallpaper, weatherboard