linchpin Meaning, Definition & Usage

  1. noun a central cohesive source of support and stability
    mainstay; backbone; lynchpin; keystone; anchor.
    • faith is his anchor
    • the keystone of campaign reform was the ban on soft money
    • he is the linchpin of this firm
  2. noun pin inserted through an axletree to hold a wheel on
    lynchpin.

WordNet

Linch"pin` noun
Etymology
AS. lynis the axletree; akin to D. luns linchpin, OS. lunisa, LG. lunse, G. lünse, OHG. lun peg, bolt.
Definitions
  1. A pin used to prevent the wheel of a vehicle from sliding off the axletree.

Webster 1913