I've seen several people saying "Hack" or "Hacking" and I just want to point out that there's a BIG difference between Hacking and modding.

Modding/Mod - Modding is a slang expression that is derived from the verb "modify". Modding refers to the act of modifying a piece of hardware or software or anything else for that matter, to perform a function not originally conceived or intended by the designer. The term modding is often used within the computer game community, particularly in regard to creating new or altered content and sharing that via the web.

Hacking/Hack - In common usage, a hacker is a person who breaks into computers, usually by gaining access to administrative controls. The subculture that has evolved around hackers is often referred to as the computer underground. Proponents claim to be motivated by artistic and political ends, and are often unconcerned about the use of illegal means to achieve them.

As you can see, There's a big difference. Hacking is illegal.

Definitions from - Wikipedia (One of the best sources)