noun
1. : a system of mountain ranges composed of tilted or uplifted fault blocks — compare basin range
2. : a system by which a railroad track is divided into short sections (as of three or four miles) and trains are so run by the guidance of electric or combined electric and pneumatic signals that (1) no train enters a section or block until the preceding train has left it or that (2) a train may be allowed to follow another into a block as long as it proceeds with extreme caution — called also respectively (1) absolute blocking, (2) permissive blocking
3. : a method of betting in draw poker comprising a 19-chip ante by the dealer, a 2-chip blind, and a 4-chip straddle