WordNet (r) 3.0 (2006):

PDA
    n 1: a lightweight consumer electronic device that looks like a
         hand-held computer but instead performs specific tasks; can
         serve as a diary or a personal database or a telephone or
         an alarm clock etc. [syn: personal digital assistant,
         PDA, personal organizer, personal organiser,
         organizer, organiser]

V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

PDA
       Personal Digital Assistant


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

Personal Digital Assistant
PDA

    (PDA) A small hand-held computer typically
   providing calendar, contacts, and note-taking applications but
   may include other applications, for example a web browser
   and media player.  Small keyboards and pen-based input
   systems are most commonly used for user input.

   The Apple Newton was a fairly early example.

   [First?  Notable examples?  Current Best?]

   (2002-09-03)