turnstile

Etymology

turn + stile

noun

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.
   The fare was fixed at 2d., irrespective of distance, and was paid by passengers on passing through turnstiles at each station. 1941 May, “Jubilee of the City Tube”, in Railway Magazine, page 224
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 ⊢ 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)". )