Breadcrumb Home > Dictionary > Index S substitution cipher: Meaning and Definition of Find definitions for: substitu'tion ci"pher Pronunciation: [key] — Cryptography. Cryptography. a cipher that replaces letters of the plain text with another set of letters or symbols. Cf. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. substitute substitution reaction TrendingHere are the facts and trivia that people are buzzing about. Chinese New Year History, Meaning, and Celebrations Current Events This Week: February 2024 Valentine's Day Valentine's Day History Mardi Gras 30 "Charlie and the Chocolate Factory" Quotes ✖ Related Content Daily Word Quiz: felicitous Analogy of the Day: Today’s Analogy Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language