The Collaborative International Dictionary of English v.0.48:

Legacy \Leg"a*cy\ (l[e^]g"[.a]*s[y^]), n.; pl. Legacies
   (-s[i^]z). [L. (assumed) legatia, for legatum, from legare to
   appoint by last will, to bequeath as a legacy, to depute: cf.
   OF. legat legacy. See Legate.]
   1. A gift of property by will, esp. of money or personal
      property; a bequest. Also Fig.; as, a legacy of dishonor
      or disease.
      [1913 Webster]

   2. A business with which one is intrusted by another; a
      commission; -- obsolete, except in the phrases last
      legacy, dying legacy, and the like.
      [1913 Webster]

            My legacy and message wherefore I am sent into the
            world.                                --Tyndale.
      [1913 Webster]

            He came and told his legacy.          --Chapman.
      [1913 Webster]

   Legacy duty, a tax paid to government on legacies.
      --Wharton.

   Legacy hunter, one who flatters and courts any one for the
      sake of a legacy.
      [1913 Webster]

WordNet (r) 3.0 (2006):

legacy
    n 1: (law) a gift of personal property by will [syn: bequest,
         legacy]

The Free On-line Dictionary of Computing (19 January 2023):

legacy system
legacy
legacy code
legacy software

    A computer system or application program which
   continues to be used because of the cost of replacing or
   redesigning it and often despite its poor competitiveness and
   compatibility with modern equivalents.  The implication is
   that the system is large, monolithic and difficult to modify.

   If legacy software only runs on antiquated hardware the cost
   of maintaining this may eventually outweigh the cost of
   replacing both the software and hardware unless some form of
   emulation or backward compatibility allows the software to
   run on new hardware.

   (1998-08-09)


The Devil's Dictionary (1881-1906):

LEGACY, n.  A gift from one who is legging it out of this vale of
tears.