The Collaborative International Dictionary of English v.0.48:

mnemonic \mnemonic\ n.
   1. Something used to assist the memory, as an easily
      remembered acronym or verse.
      [WordNet 1.5]

   2. An abbreviated word that resembles the full word, used so
      as to be easily recognized; as, the CIDE uses ... tags as
      mnemnonics for an italicised word or field.
      [PJC]

   Note: In basic organic chemistry class, one may learn the
         mnenomic "Oh my, such good apple pie" to help remember
         the names of the dicarboxylic acids in increasing order
         of length, namely: oxalic, malonic, succinic, glutaric,
         adipic, and pimelic acids. (From L. Fieser's Organic
         Chemistry text).

The Collaborative International Dictionary of English v.0.48:

Mnemonic \Mne*mon"ic\ (n[-e]*m[o^]n"[i^]k), Mnemonical
\Mne*mon"ic*al\ (n[-e]*m[o^]n"[i^]*kal), a. [Gr. mnhmoniko`s,
   fr. mnh`mwn mindful, remembering, mnh`mh memory, mna^sqai to
   think on, remember; akin to E. mind.]
   Assisting in memory; helping to remember; as, a mnemonic
   device.
   [1913 Webster]

WordNet (r) 3.0 (2006):

mnemonic
    adj 1: of or relating to or involved the practice of aiding the
           memory; "mnemonic device" [syn: mnemonic,
           mnemotechnic, mnemotechnical]
    n 1: a device (such as a rhyme or acronym) used to aid recall

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

mnemonic

    A word or string which is intended to be easier
   to remember than the thing it stands for.  Most often used in
   "instruction mnemonic" which are so called because they are
   easier to remember than the binary patterns they stand for.
   Non-printing ASCII characters also have mnemonics like
   NAK, ESC, DEL intended to evoke their meaning on certain
   systems.

   (1995-05-11)