Obsolete To detach (an artillery piece) from its limber to deploy for firing.
The gun he drove had been unlimbered near Horsell, in order to command the sand-pits, and its arrival had precipitated the action.1895–1897, H[erbert] G[eorge] Wells, “At the Window”, in The War of the Worlds, London: William Heinemann, published 1898, →OCLC, book I (The Coming of the Martians), page 83:
2
Broadly To clumsily put into employ (a large weapon or object).
3
Broadly To unsling (something, as a backpack, carried on the body with a strap); to bring (something carried) into the hands for use.
4
Figuratively To stretch (limbs, muscles, etc., that have been cramped or unused for some time).
"I fancy," said Psmith, "that this is one of those moments when it is necessary for me to unlimber my Sherlock Holmes system. […] Do you follow me, Comrade Maloney?" / "That's right," said Billy Windsor. "Of course." / "Elementary, my dear Watson, elementary," murmured Psmith.1909 October – 1910 February, P[elham] G[renville] Wodehouse, “In Pleasant Street”, in Psmith Journalist, London: A[dam] & C[harles] Black, […], published October 1923, →OCLC, page 140:
Bony jumped down and unlimbered his cramped muscles before going after his camels.1963, Arthur Upfield, The Lake Frome Monster, London: Pan Books, published 1969, page 111: