WordNet (r) 3.0 (2006):

applet
    n 1: a Java application; an application program that uses the
         client's web browser to provide a user interface

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

applet

    A Java program which can be distributed as
   an attachment in a web document and executed by a
   Java-enabled web browser such as Sun's HotJava,
   Netscape Navigator version 2.0, or Internet Explorer.

   Navigator severely restricts the applet's file system and
   network access in order to prevent accidental or deliberate
   security violations.  Full Java applications, which run
   outside of the browser, do not have these restrictions.

   Web browsers can also be extended with plug-ins though these
   differ from applets in that they usually require manual
   installation and are platform-specific.  Various other
   languages can now be embedded within HTML documents, the
   most common being JavaScript.

   Despite Java's aim to be a "write once, run anywhere"
   language, the difficulty of accomodating the variety of
   browsers in use on the Internet has led many to abandon
   client-side processing in favour of server-side Java
   programs for which the term servlet was coined.

   Merriam Webster "Collegiate Edition" gives a 1990 definition:
   a short application program especially for performing a simple
   specific task.

   (2002-07-12)