The Collaborative International Dictionary of English v.0.48:

Postscript \Post"script\, n. [L. postscriptus, (assumed) p. p.
   of postscribere to write after; post after + scribere to
   write: cf. F. postscriptum. See Post-, and Scribe.]
   A paragraph added to a letter after it is concluded and
   signed by the writer; an addition made to a book or
   composition after the main body of the work has been
   finished, containing something omitted, or something new
   occurring to the writer. [Abbrev. P. S.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

postscript
    n 1: a note appended to a letter after the signature [syn:
         postscript, PS]
    2: textual matter that is added onto a publication; usually at
       the end [syn: addendum, supplement, postscript]

Moby Thesaurus II by Grady Ward, 1.0:

53 Moby Thesaurus words for "postscript":
   PS, Parthian shot, addendum, affix, afterthought, allonge,
   appendix, back matter, chorus, coda, codicil, colophon, commentary,
   conclusion, consequence, continuance, continuation, double take,
   dying words, enclitic, envoi, epilogue, follow-through, follow-up,
   infix, interlineation, interpolation, last words, marginalia, note,
   parting shot, peroration, postface, postfix, postlude, prefix,
   proclitic, refrain, rider, scholia, second thought, sequel,
   sequela, sequelae, sequelant, sequent, sequitur, subscript, suffix,
   supplement, swan song, tag, tail



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

PostScript
 n.

    A page description language, based on work originally done by John Gaffney
    at Evans and Sutherland in 1976, evolving through ?JaM? (?John and Martin?,
    Martin Newell) at XEROX PARC, and finally implemented in its current form
    by John Warnock et al. after he and Chuck Geschke founded Adobe Systems
    Incorporated in 1982. PostScript gets its leverage by using a full
    programming language, rather than a series of low-level escape sequences,
    to describe an image to be printed on a laser printer or other output
    device (in this it parallels EMACS, which exploited a similar insight
    about editing tasks). It is also noteworthy for implementing on-the fly
    rasterization, from Bezier curve descriptions, of high-quality fonts at low
    (e.g. 300 dpi) resolution (it was formerly believed that hand-tuned bitmap
    fonts were required for this task). Hackers consider PostScript to be among
    the most elegant hacks of all time, and the combination of technical merits
    and widespread availability has made PostScript the language of choice for
    graphical output.


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

PostScript

    A page description language based
   on work originally done by John Gaffney at Evans and
   Sutherland in 1976, evolving through "JaM" ("John and Martin",
   Martin Newell) at XEROX PARC, and finally implemented in its
   current form by John Warnock et al. after he and Chuck Geschke
   founded Adobe Systems, Inc. in 1982.

   PostScript is an interpreted, stack-based language (like
   FORTH).  It was used as a page description language by the
   Apple LaserWriter, and now many laser printers and
   on-screen graphics systems.  Its primary application is to
   describe the appearance of text, graphical shapes, and sampled
   images on printed or displayed pages.

   A program in PostScript can communicate a document description
   from a composition system to a printing system in a
   device-independent way.

   PostScript is an unusually powerful printer language because
   it is a full programming language, rather than a series of
   low-level escape sequences.  (In this it parallels Emacs,
   which exploited a similar insight about editing tasks).  It is
   also noteworthy for implementing on-the fly rasterisation,
   from Bezier curve descriptions, of high-quality fonts at
   low (e.g. 300 dpi) resolution (it was formerly believed that
   hand-tuned bitmap fonts were required for this task).

   PostScript's combination of technical merits and widespread
   availability made it the language of choice for graphical
   output until PDF appeared.

   The Postscript point, 1/72 inch, is slightly different from
   other point units.

   An introduction

(http://cs.indiana.edu/docproject/programming/postscript/postscript.html).

   ["PostScript Language Reference Manual" ("The Red Book"),
   Adobe Systems, A-W 1985].

   [Jargon File]

   (2002-03-11)