[1] : The Collaborative International Dictionary of English v.0.48

mainmast \main"mast`\, n. naut.
   the principal mast in a ship or other vessel.
   1913 webster

[2] : The Collaborative International Dictionary of English v.0.48

mast \mast\, n. as. maest, masc.; akin to d., g., dan.,  sw.
   mast, icel. mastr, and perh. to l. malus.
   1913 webster
   1. naut. a pole, or long, strong, round piece of timber, or
      spar, set upright in a boat or vessel, to sustain the
      sails, yards, rigging, etc. a mast may also consist of
      several pieces of timber united by iron bands, or of a
      hollow pillar of iron or steel.
      1913 webster

            the tallest pine
            hewn on norwegian hills, to be the mast
            of some great ammiral.                --milton.
      1913 webster

   note: the most common general names of masts are foremast,
         mainmast, and mizzenmast, each of which may be made
         of separate spars.
         1913 webster

   2. mach. the vertical post of a derrick or crane.
      1913 webster

   3. aeronautics a spar or strut to which tie wires or guys
      are attached for stiffening purposes.
      webster 1913 suppl.

   afore the mast, before the mast. see under afore, and
      before.

   mast coat. see under coat.

   mast hoop, one of a number of hoops attached to the fore
      edge of a boom sail, which slip on the mast as the sail is
      raised or lowered; also, one of the iron hoops used in
      making a made mast. see made.
      1913 webster
see also:
foremast mainmast mizzenmast afore the mast before the mast afore 
before mast coat coat mast hoop made 

[3] : WordNet (r) 2.0

mainmast
     n : the chief mast of a sailing vessel with two or more masts

Mainmast >> M Words
Mainmast, definition of term: Mainmast
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