I've removed this text, which belongs under "jack up", not "jack":
-- Paul G 20:52, 14 Feb 2004 (UTC)
How about as a shortening of carjack? — This comment was unsigned.
Hijack is 1920's and is an original term, "carjack" is a portmanteau of "car" and "hijack" and it seems most likely that the modern "jack" is a contraction of "carjack" but good luck proving THAT as "jack" as a contraction of "hijack" was around but fell into disuse.
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Rfv-sense: baseball slang interjection. DCDuring TALK 16:37, 7 July 2009 (UTC)
RFV failed, interjection removed. Anyone wishing to add the noun, please feel free. —RuakhTALK 13:17, 29 August 2010 (UTC)
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A jumble, especially of etymologies. DCDuring TALK 13:35, 20 December 2008 (UTC)
transitive verb: to open something by prying it apart (slang) Microsoft® Encarta® 2009
--Backinstadiums (talk) 18:34, 28 May 2020 (UTC)
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Rfv-sense: Noun (baseball) A home run.
I didn't find such a definition at “jack”, in OneLook Dictionary Search.. It does appear in some on-line glossaries, including w:Glossary of baseball. It appears in some blogs, but not in Books or UseNet. DCDuring (talk) 19:43, 28 May 2020 (UTC)
RFV-passed Kiwima (talk) 19:35, 7 June 2020 (UTC)
a jack is a kind of flag, but https://newspapers.com/image/583604029 seems to also use it as a synonym for 'canton'. Arlo Barnes (talk) 08:33, 16 May 2023 (UTC)