1. participant or contributor, share knowledge
Professional
Social
not party to that information, interested/political/third party
To 'be party to something' means to be a part of it. If you are party to something you are aware of what is going on or you are a participant or a contributor to something. To be a party to something can be another way of asking someone about their involvement in a deed or a project. This is quite a formal expression used often in legal contexts.