Noun

1. A state of balance; equilibrium.
   • 1794, Edmund Burke, A Letter to a Noble Lord,

     Government was unnerved, confounded, and in a manner suspended. Its equipoise was totally gone.

   • 1869, T. S. Arthur, After the Storm, Ch. IV,

     “An easy evasion”, retorted the excited bride, who had lost her mental equipoise.

   • 1878, Thomas Hardy, The Return of the Native, Ch. 6,

     The words were not without emotion, and retained their level tone as if by a careful equipoise between imminent extremes.

   • 1927-29, Mahatma Gandhi, An Autobiography or The Story of my Experiments with Truth, Part II, Raychandbhai, translated 1940 by Mahadev Desai,

     And I saw him thus absorbed in godly pursuits in the midst of business, not once or twice, but very often. I never saw him lose his state of equipoise.

2. A counterbalance.
   • 1911, H. G. Wells, The Cone,

     The cone’s not fixed, it’s hung by a chain from a lever, and balanced by an equipoise.

Verb

1. To act or make to act as an equipoise.
2. To cause to be or stay in equipoise.