The mathematical symbol (0) denoting absence of quantity; zero. An Arabic numeral or figure; a number. One having no influence or value; a nonentity. A cryptographic system in which units of text of regular length, usually letters, are transposed or substituted according to a predetermined code. The key to such a system. A message written or transmitted in such a system. A design combining or interweaving letters or initials; a monogram. To put in secret writing; encode. To solve by means of arithmetic.