The Collaborative International Dictionary of English v.0.48:

deprecate \dep"re*cate\ (d[e^]p"r[-e]*k[=a]t), v. t. [imp. & p.
   p. Deprecated (-k[=a]`t[e^]d); p. pr. & vb. n.
   Deprecating (-k[=a]`t[i^]ng).] [L. deprecatus, p. p. of
   deprecari to avert by prayer, to deprecate; de- + precari to
   pray. See Pray.]
   To pray against, as an evil; to seek to avert by prayer; to
   seek deliverance from; to express deep regret for; to desire
   the removal of. [archaic]
   [1913 Webster]

   2. To protest against; to advance reasons against.
      [PJC]

            His purpose was deprecated by all round him, and he
            was with difficulty induced to adandon it. --Sir W.
                                                  Scott.
      [1913 Webster]

   3. To disapprove of strongly; to express a low opinion of.
      [PJC]

The Jargon File (version 4.4.7, 29 Dec 2003):

deprecated
 adj.

    Said of a program or feature that is considered obsolescent and in the
    process of being phased out, usually in favor of a specified replacement.
    Deprecated features can, unfortunately, linger on for many years. This term
    appears with distressing frequency in standards documents when the
    committees writing the documents realize that large amounts of extant (and
    presumably happily working) code depend on the feature(s) that have passed
    out of favor. See also dusty deck.

    [Usage note: don't confuse this word with ?depreciated?, or the verb form
    ?deprecate? with ?depreciate?. They are different words; see any dictionary
    for discussion.]


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

deprecated

   Said of a program or feature that is considered obsolescent
   and in the process of being phased out, usually in favour of a
   specified replacement.  Deprecated features can,
   unfortunately, linger on for many years.  This term appears
   with distressing frequency in standards documents when the
   committees writing the documents realise that large amounts of
   extant (and presumably happily working) code depend on the
   feature(s) that have passed out of favour.

   See also dusty deck.

   [Jargon File]

   (1995-04-19)