What does BETA mean?

A beta version is the first version released outside the organization or community that develops the software, for the purpose of evaluation or real-world black/grey-box testing. The process of delivering a beta version to the users is called beta release. Beta level software is between 60% and 70% complete, generally includes all features, but may also include known issues and bugs of a less serious variety.

Another answer:

BETA is a pure object-oriented language originating within the "Scandinavian School" in object-orientation where the first object-oriented language Simula was developed.

From a technical perspective, BETA provides the following unique feature:

Classes and Procedures are unified to one concept, a Pattern.
Classes are defined as properties/attributes of objects. This means that a class cannot be instantiated without an explicit object context.
A consequence of the above is that BETA supports nested classes; and BETA's nested classes are indeed one of the primary sources of inspiration for Java's inner classes.
Classes can be virtually defined (much like virtual methods can in most other object-oriented programming languages).
Virtual entities (such as methods and classes) are never overwritten; instead they are refined or specialized.

BETA supports the object-oriented perspective on programming and contains comprehensive facilities for procedural and functional programming. BETA has powerful abstraction mechanisms for supporting identification of objects, classification and composition. BETA is a strongly typed language like Simula, Eiffel and C++, with most of the type checking being carried out at compile-time. It is well known that it is not possible to obtain complete type checking at compile-time without sacrificing the expressiveness of the language. BETA aims to achieve an optimum balance between compile-time type checking and run-time type checking.

Another view on Beta

It's a term that's used to describe how far a product has moved along the development cycle.
Technically, a Beta device or application isn't considered to be a mature product. A Beta device has been through internal company review and error testing, but it hasn't been thoroughly tested by people outside of the development team.
Beta products can be great, and you just get to play with something new, or if they development team wasn't the best, a Beta product can be a real pain in the ^&*.

More Beta

BETA in computer terms, generally means, its still in test.

A software company writes a program, and has it tested by their inhouse engineers. Once they have finished testing, it is released to users as a beta version. Reason being, the in house engineers, simply dont have the time to test every last thing about any given program.

Each user will use the program for different things. Example being a cleaning program.

Users can say which files they want the program to find and clean. Some may only want the pc to clean the recycle bin. Others will say, I want all temporary internet files cleaned, but leave the recycle bin alone. Another could say, right clean the bin, clean the temp files, i also want all Jpegs gone, but leave the gif's.

If a error occurs during this process, it usually appears on screen, where you can then tell the software company.

After a certain time, when all these errors (bugs) have been found and fixed they will release the full version.

Some companies, release beta versions to known members specifically for testing.