I hear what you're saying, although I think I do make this effort. But after the 5th of 6th time I'm interrupted halfway through a sentence, usually by the same person who's been essentially thinking out loud for 80% of the meeting, I run out of steam and just give up.

This is what I mean by 'making room'. I'm not expecting people to ask me what I think, or for everyone to take turns or something silly like that. But I do think that if other participants are incapable of 'playing nice' then the senior person in the room, who's essentially 'chairing' the meeting, should jump in at some point. Or maybe my contributions aren't as valuable as I think. Who knows.

I really don't know how to deal with this kind of situation on my own. I've tried everything. The only thing that has ever really worked is the hyper-aggressive "excuse me, I wasn't finished", spoken at a volume slightly louder than the person interrupting (so basically shouting).

I don't want to do that sort of thing. Sure, it works, but it also makes the rest of the meeting very uncomfortable and unpleasant for all involved. And I suspect if done more than a few times I'll end up with a pretty bad reputation (not to mention an enemy or two, for little gain). Believe me, I'm not a timid person and I'm not afraid to speak my mind. If I have to make an enemy to get something important done, I will. But, if given the choice, I'd strongly prefer that adults speak to one another in a civilised manner.

I pretty much just avoid meetings now, if I can.