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

linchpin \linch"pin`\ li^nch"pi^n`, n. as. lynis the
   axletree; akin to d. luns linchpin, os. lunisa, lg. lunse, g.
   l"unse, ohg. lun peg, bolt.
   a pin used to prevent the wheel of a vehicle from sliding off
   the axletree.
   1913 webster

[2] : WordNet (r) 2.0

linchpin
     n 1: 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, mainstay, keystone, backbone, lynchpin
     2: pin inserted through an axletree to hold a wheel on syn: lynchpin
see also:
anchor mainstay keystone backbone lynchpin 

Linchpin >> L Words
Linchpin, definition of term: Linchpin
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