The Collaborative International Dictionary of English v.0.48:

encryption \encryption\ n.
   the process of converting messages in ordinary language, or
   other information into a secret coded form that cannot be
   interpreted without knowing the secret method for
   interpretation, called the key.

   Note: Encryption is used commonly to allow messages to be
         transmitted between parties at a distance without
         permitting others to read and understand the message.
         It is also used to make data more secure from possible
         discovery and uninterpretable by unauthorized people
         accessing the data. In order to read an encrypted
         message, a party normally requires knowledge of both
         the method of encryption and the secret key, which may
         be a single word or more complex sequence of
         characters. Until recently, transmission of such secret
         messages required that the key be transmitted secretly
         by some seecure and reliable method to the party
         receiving the message. More recently, a mathematical
         method was discovered to allow a party to publish an
         encoding key (the public key) which allows anyone to
         encode a message, but the message thus encoded can only
         be decoded by the person possessing a corresponding
         key, called the private key. This two-key system is
         called the public-key encryption method.

   Syn: encoding, coding, enciphering, ciphering, cyphering,
        writing in code.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

encryption
    n 1: the activity of converting data or information into code
         [syn: encoding, encryption]

The Free On-line Dictionary of Computing (30 December 2018):

encryption

    Any procedure used in cryptography
   to convert plaintext into ciphertext (encrypted message)
   in order to prevent any but the intended recipient from
   reading that data.

   Schematically, there are two classes of encryption primitives:
   public-key cryptography and private-key cryptography; they
   are generally used complementarily.
   Public-key encryption algorithms include RSA;
   private-key algorithms include the obsolescent Data Encryption
   Standard, the Advanced Encryption Standard, as well as
   RC4.

   The Unix command crypt performs a weak form of encryption.
   Stronger encryption programs include Pretty Good Privacy and
   the GNU Privacy Guard.

   Other closely related aspects of cryptograph include
   message digests.

   (2003-04-12)