knuckle
noun
a joint of a finger, especially one of the articulations of a metacarpal with a phalanx.
Used to describe an action that will be fully completed or achieved by a specific point in the future.
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
Then the chances are you will be in the thick of it, Somerton, for by August there will either be war, or old Kruger will have knuckled under.
From With Rifle and Bayonet A Story of the Boer War by F. S. (Frederick Sadleir) Brereton