taper pin

noun

a short round metal rod having a small amount of taper so that when driven into a hole it tightens on the taper so that it can act as a stop or wedge

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012