See also: turn-stile
turnstile (plural turnstiles)
- 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.
- A similar device in a footpath to allow people through one at a time while preventing the passage of cattle.
- (mathematics, logic) The 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)"  or "give(s)". )
- (mathematics, logic): double turnstile
rotating mechanical device