Wiktionary
n. A Mac OS scripting tool used to create scripts and applets.
Wikipedia
AppleScript is a scripting language created by Apple Inc. and built into Macintosh operating systems since System 7. The term "AppleScript" may refer to the scripting system itself, or to an individual script written in the AppleScript language.
AppleScript is primarily a scripting language developed by Apple to do Inter-Application Communication (IAC) using AppleEvents. AppleScript is related to, but different from, AppleEvents. AppleEvents is designed to exchange data between and control other applications in order to automate repetitive tasks. AppleScript has some limited processing abilities of its own, in addition to sending and receiving AppleEvents to applications. AppleScript can do basic calculations and complex text processing, and is extensible, allowing the use of scripting additions that add new functions to the language. Mainly, however, AppleScript relies on the functionality of applications and processes to handle complex tasks. As a structured command language, AppleScript can be compared to Unix shells, the Microsoft Windows Script Host, or IBM REXX in its functionality, but it is unique from all three. Essential to its functionality is the fact that Macintosh applications publish "dictionaries" of addressable objects and operations.
AppleScript has some elements of object-oriented programming, particularly in the construction of script objects, and natural language programming tendencies in its syntax, but does not strictly conform to either category.