turnstile

turn +‎ stile

A set of turnstiles in the USA

• (UK) IPA^(key): /ˈtɜːnstaɪl/
• (US) IPA^(key): /ˈtɝnstaɪl/

• Audio (US)

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turnstile (plural turnstiles)

1. A rotating mechanical device that controls and counts passage between public areas, especially one that only allows passage after a charge has been paid.
   • 1941 May, “Jubilee of the City Tube”, in Railway Magazine, page 224:

     The fare was fixed at 2d., irrespective of distance, and was paid by passengers on passing through turnstiles at each station.

2. A similar device in a footpath to allow people through one at a time while preventing the passage of cattle.
3. (mathematics, logic) The ${\displaystyle \vdash }$ symbol used to represent logical entailment (deducibility relation), especially of the syntactic type; i.e., syntactic consequence. (Such symbol can be read as "prove(s)" [1] or "give(s)". [2])

• (mathematics, logic): double turnstile