What is the right definition of agnostic?

[robvalue]

*Sorry if this is in the wrong section*
I've been reading some comments on social media where people claim to be neither theist nor atheist but agnostic, i was under the impression that a/theism is about belief and a/gnostic is about knowledge.

When i googles 'agnostic' the first thing that came up was this:

ag·nos·tic
aɡˈnästik/
noun
noun: agnostic; plural noun: agnostics

1. 1.
   a person who believes that nothing is known or can be known of the existence or nature of God or of anything beyond material phenomena; a person who claims neither faith nor disbelief in God.
   synonyms:
   skeptic, doubter, doubting Thomas, cynic; More
   unbeliever, nonbeliever, rationalist;
   rarenullifidian
   "as far as I know, Stevens was an atheist, or at least an agnostic"
   
   
   antonyms:
   believer, theist
   

adjective
adjective: agnostic
1.
of or relating to agnostics or agnosticism.
synonyms:
skeptic, doubter, doubting Thomas, cynic; More

So what is the right definition? And if the google definition is wrong, why haven't they fixed it? It's basically spreading false information and a lot of people rely on Google.

I have underlined what is generally accepted to be the right definition. I don't know why it has the alternative, which is basically the most common misuse of the word.

I have written more about it in my website here. I've also done a video and an accompanying chart:

https://www.youtube.com/watch?v=d34BmGnrUEI