TURNSTILE
turnstile
(noun) a gate consisting of a post that acts as a pivot for rotating arms; set in a passageway for controlling the persons entering
Source: WordNet® 3.1
Etymology
Noun
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.
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)". )
Source: Wiktionary
Turn"stile`, n.
1. A revolving frame in a footpath, preventing the passage of horses
or cattle, but admitting that of persons; a turnpike. See Turnpike,
n., 1.
2. A similar arrangement for registering the number of persons
passing through a gateway, doorway, or the like.
Source: Webster’s Unabridged Dictionary 1913 Edition