Feel free to add more answers. This market will be resolved by a poll or another appropriate method if/when the time comes. I may bet on this market.
@MugaSofer In general, I think AGI can be defined as artificial intelligence with a human-level or greater capability that can apply its intelligence to general problems and situations independently.
For the purpose of this market, I think it's best to leave the definition to the time of resolution. Meaning that if/when someone claims that AGI exists and the question should be resolved, the polls (or similar) ask both if AGI exists and if the relevant statements are true.
@NathanF While it's true that the market may never resolve, I don't think any of the answers would necessarily mean Manifold or its users would no longer exist. I think all possible resolutions for this market (given the currently existing answers) could theoretically be true while Manifold and its users survive. Even if AGI exists and is not friendly to humans, for example, it doesn't necessarily mean it would exterminate all Manifold users or destroy Manifold.