Definition of "equipoise"

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

1796, Edmund Burke, A Letter from the Right Honourable Edmund Burke to a Noble Lord, on the Attacks Made upon Him and His Pension

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

1869, T. S. Arthur, chapter IV, in After the Storm

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

1878 January–December, Thomas Hardy, “The Figure against the Sky”, in The Return of the Native […], volume I, London: Smith, Elder, & Co., […], published 1878, book I (The Three Women), page 135

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.

1927–1929, M[ohandas] K[aramchand] Gandhi, “Raychandbhai”, in The Story of My Experiments with Truth: Translated from the Original in Gujarati, volumes (please specify |volume=I or II), Ahmedabad, Gujarat: Navajivan Press

To my mind, the textual arguments in this case are close to equipoise.

2021, Ronald Mann, Justices to consider awards of costs of appellate litigation, SCOTUSblog (Apr. 20, 2021)

Perhaps that quality which existed, in spite of the equipoise against it, in Sir Howard, was fidelity in friendship.

1838, [Letitia Elizabeth] Landon (indicated as editor), chapter XI, in Duty and Inclination: […], volume III, London: Henry Colburn, […], page 136

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

1895 September 18, H[erbert] G[eorge] Wells, “The Cone”, in The Plattner Story and Others, London: Methuen & Co. […], published March 1897, page 188