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

mainstay \main"stay`\, n.
   1. naut. the stay extending from the foot of the foremast
      to the maintop.
      1913 webster

   2. main support; principal dependence.
      1913 webster

            the great mainstay of the church.     --buckle.
      1913 webster

[2] : WordNet (r) 2.0

mainstay
     n 1: a prominent supporter; "he is a pillar of the community"
          syn: pillar
     2: a central cohesive source of support and stability; "faith
        is his anchor"; "the keystone of campaign reform was the
        ban on soft money"; "he is the linchpin of this firm"
        syn: anchor, keystone, backbone, linchpin, lynchpin
     3: the forestay that braces the mainmast
see also:
pillar anchor keystone backbone linchpin lynchpin 

[3] : Moby Thesaurus II by Grady Ward, 1.0

124 moby thesaurus words for "mainstay":
   maecenas, abettor, admirer, advocate, afford support, aficionado,
   alpenstock, angel, apologist, arm, athletic supporter, back,
   back up, backbone, backer, backing, bandeau, bear, bear up, bearer,
   bolster, bolster up, bra, brace, bracer, bracket, brassiere, buff,
   bulwark, buoy up, buttress, cane, carrier, carry, cervix, champion,
   corset, cradle, crook, crutch, cushion, defender, dependence,
   encourager, endorser, exponent, fan, favorer, foundation garment,
   friend at court, fulcrum, girdle, give support, guy, guywire, hold,
   hold up, jock, jockstrap, keep afloat, keep up, lend support,
   lover, main strength, maintain, maintainer, mast, neck, paranymph,
   partisan, patron, pillar, pillow, promoter, prop, protagonist,
   reinforce, reinforcement, reinforcer, reliance, rest,
   resting place, rigging, second, seconder, sectary, sheet anchor,
   shore, shore up, shoulder, shroud, sider, sinews, spine, sponsor,
   sprit, staff, stalwart, standby, standing rigging, stave, stay,
   stick, stiffener, strengthener, subsidize, subvention, support,
   supporter, sustain, sustainer, sympathizer, underbrace, undergird,
   underlie, underpin, underset, upbear, uphold, upholder, upkeep,
   votary, walking stick, well-wisher

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