WordNet (r) 3.0 (2006):

checksum
    n 1: a digit representing the sum of the digits in an instance
         of digital data; used to check whether errors have occurred
         in transmission or storage

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

checksum

    A computed value which depends on
   the contents of a block of data and which is transmitted or
   stored along with the data in order to detect corruption of
   the data.  The receiving system recomputes the checksum based
   upon the received data and compares this value with the one
   sent with the data.  If the two values are the same, the
   receiver has some confidence that the data was received
   correctly.

   The checksum may be 8 bits (modulo 256 sum), 16, 32, or some
   other size.  It is computed by summing the bytes or words of
   the data block ignoring overflow.  The checksum may be
   negated so that the total of the data words plus the checksum
   is zero.

   Internet packets use a 32-bit checksum.

   See also digital signature, cyclic redundancy check.

   (1996-03-01)