STD code

noun
  1. British a code of four or more digits, other than those comprising a subscriber's local telephone number, that determines the routing of a call

Word Origin for STD code

C20: s (ubscriber) t (runk) d (ialling)
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