OpenAI's original definition for AGI is as follows:

"By AGI, we mean highly autonomous systems that outperform humans at most economically valuable work."

Here is a diagram illustrating the governance structure of OpenAI:

The following is a quote from the original post by OpenAI, 

Fifth, the board determines when we've attained AGI. Again, by AGI we mean a highly autonomous system that outperforms humans at most economically valuable work. Such a system is excluded from IP licenses and other commercial terms with Microsoft, which only apply to pre-AGI technology.

An action that would "hint at" OpenAI achieving AGI would be the exclusion of a specific state of the art AI system from IP licenses and other commercial terms with Microsoft while their partnership with Microsoft remains more or less the same structurally (although the composition might change). 

Same market for a longer time-frame is below: