Question: Throughout both my academic and professional career I've encountered situations where in such roles (as most of us would have), where as a happy go lucky graduate who doesn't know it all (but thought I did) would attend meetings and I wouldn't know what certain industry terminology meant or understood certain aspects of the project cycle.

I would become really pedantic about asking stupid questions that should be (what I felt) well known. But, I wouldn't ask them in the meeting (especially in a group setting) purposely to not look stupid.

To overcome this I would do two things:

* I would always go home (after the day is done) and look up the terminology/subject matter and teach myself that way, so if the topic comes up again I'd be armed with the newly obtained knowledge.
* I would wait until my superior came up to me and if they mentioned it, I would have a look of confusion on my face and then ask the question. (But this to me, seemed like I wasn't listening in the meeting and/or unprofessional).

Which made me contemplate the best time to ask these questions to make myself seem less like I wasn't paying attention but more because I'm willing to learn.

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So, when is it okay to ask "stupid" questions in the workplace?

Answer: 
In your shoes, besides thinking about "when" to ask, I would think about *who* to ask.

Your instinct of waiting until you are "offline" to ask is a good one. Unless you absolutely "need to" (you are one of the principal participants), you don't want to ask questions in front of a lot of people at a meeting.

So the other issue is who to ask. Usually, that person is your boss. The reason is, the boss has the greatest stake in your development; the better you are, the better s/he is. A good boss will recognize that and try to accommodate your questions.

There are some situations when you have a bad boss, or one who favors another co-worker over you, which would (largely) rule out that option.

Who else can you ask? Basically, someone you can trust. Possibly a peer or co-worker, possibly a prospective (or actual) mentor. Executives have been known to confide in secretaries or janitors, and find that these people are more knowledgeable than they would have guessed. 

Having focused on who to ask, the question of "when to ask" is answered by "at a good time for them."

The reason I emphasize "who" comes from Michael Lewis' "Liar's Poker." Someone asked a trainer, "how do you become successful at Salomon Brothers?" The trainer thought about it and said something like, "Most of you are going about it wrong. You are asking yourselves what you want. You should be asking yourself who you want. It's a jungle out there. So figure out who is willing to "adopt" you and help you advance in the company." And then ask them what you need to know.
Your question seems to be directed towards meetings specifically, and not so much towards a classroom/group setting ... that being said,

I suggest you ask for an agenda in advance for the meetings to which you are attending. Meetings should have an agenda anyway to keep people on task and efficient. 

This will give you the necessary time to prepare yourself to give as much concise contribution as possible which will increase your value to everybody else in attendance.

The purpose of a meeting is to allow collaboration and input from individuals and/or a place to give instruction. If you foresee an unclear subject matter that could affect how you do your work, and you've done what time permits to delve into it beforehand, then there is no 'shame' in asking a 'stupid' question.

If you've requested preparatory information and were not given it, and such an unclear topic comes up in conversation during the meeting, go ahead and ask the 'stupid' question. Meetings bring together individuals that are really good at different things as to get the best ideas brought forward. Not everybody in the room will have your jargon or perspective, just as you don't have theirs; it's part of the purpose of having a meeting. With proper preparation on the meeting planners part the little questions won't need to be asked, but it happens, and when it does, don't feel bad for asking. 

Companies also have their own jargon and way of doing things, many people come from other companies that have different procedures and traditions. If you are newer to a group that has always done their own thing a certain way, it wouldn't hurt to pull somebody aside (a new friend?) after the meeting and explain to them the unfamiliarity of your circumstance and ask them if they can clarify some things, with a follow up of asking if that person can be approached in similar circumstances in the future. This will also provide perspective for this person to recognize situations which may be a bit unclear for you and provide an opportunity for him to help with the clarity during the actual meeting.

I must note though that many items on a meeting's agenda won't apply to everybody. If the subject material at hand doesn't apply to yourself, then don't interrupt the flow of conversation to ask to get the question/material clarified that doesn't apply to yourself.