Every field has its jargon. Game designers will happily talk about HUDs and avatars and positive feedback loops, oblivious to the fact that most people who haven't been doing this for the last few years of their career might have no idea what they're talking about. This is a particular danger when teaching, by the way, that you lapse into "designer-speak" without defining your terms, only to be met with blank stares.
People in academia do this too, and it can sometimes be confusing for the new designer-turned-teacher to keep up. A recent discussion on the IGDA game educators mailing list reminded me that one of the new terms an industry person is likely to run into is the terminal degree.
(Disclaimer: since I've only been doing this the last couple of years, I might get some details wrong. If you see any errors, feel free to post in the comments and I'll fix the post. Thank you.)
What is a terminal degree? The best description I can think of is a degree higher than Bachelor's, which is the highest degree offered, at the institution you received it, at the time you received it. Normally this means a Ph.D., but some fields don't offer one (the best-known are probably MFA and MBA) so those are referred to as terminal Master's degrees. Typically, a non-terminal Master's takes less time than a terminal Master's, which takes less time than a Ph.D. (in case you're trying to get an advanced degree as fast as possible).
Edit: Looks like I was wrong about this, it's just the highest degree offered in a field -- still, usually a Ph.D. but in some fields an MFA, or other degree. I'm not sure what happens at boundary conditions, such as if you get an MFA in Game Design (the highest degree offered today) and then one school decides to offer a Ph.D. in Game Design. Does that invalidate the 'terminality' of these other degrees?
Note that this means that if a new Ph.D. is offered at a university that previously only offered a Master's, whether the Master's is terminal or not is based on when the student enrolled; if you started before the Ph.D. was available, it's terminal. Timing matters.
Why should you care? Terminal degrees are important if you're planning to make a career of teaching. Having one means that you get paid more; at some places it's even a requirement for certain positions. If you don't have one already, think about getting one. Unfortunately, leaving a full-time career in industry to go back to graduate school is difficult for most people. Fortunately, once you do have a full-time job at a university, one of the more common benefits is being able to take classes for free or almost-free; if it's not practical to get your terminal degree first, it's quite possible to get it second.
From seeing a number of people going through graduate school, I also secretly suspect that it's called a "terminal degree" because it has a good chance of killing you.