Everything, the full range of possibilities, as in He ordered a pizza with the works, or All right, tell me, give me the works on it. This usage derives from works in the sense of "a complete set of parts for a machine or mechanism." [Colloquial; late 1800s]
A beating or other severe treatment. This usage is often put as give someone the works, as in They took him outside and gave him the works. [Slang; first half of 1900s]
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