| Noun | 1. | Social Security number - the number of a particular individual's Social Security account identification number, number - a numeral or string of numerals that is used for identification; "she refused to give them her Social Security number" U.S.A., United States, United States of America, US, USA, America, the States, U.S. - North American republic containing 50 states - 48 conterminous states in North America plus Alaska in northwest North America and the Hawaiian Islands in the Pacific Ocean; achieved independence in 1776 |