Word meanings

I've been having a debate with a gentleman on YouTube. He has ignored the original subject of the post and has instead decided to focus on semantics. In particular my usage of certain words, could you please help me clarify these words.

I used omnipotent to describe a being that is capable of doing anything (including knowing anything), he responded by saying that the word omniscient was the correct terminology.

He also replied that the being I was referring to was not described as omnipotent or omniscient to begin with - but he is referred to as all powerful, limitless, knowing all. Because of this he says that the terminology I used is incorrect.

He informs me that omniscient, omnipotent, all knowing, all powerful are quite different words with different meanings and that nobody in their right mind would use them in place of the other.

He said this being was without definition and beyond our understanding, he goes into say it is limitless. I told him limitless IS giving something definition, therefore it able to be defined.

He tells me that to define something about the being is to 'set bounds to' and can't be used to simply describe the being. He assures me words can only have one meaning.

He says that any respectable dictionary will use only the root of the word to provide a definition of a word.

He says that define and describe can not ever be used interchangeably, no matter the circumstances. He is adamant that words cannot have the same meaning and only one word will ever fit a certain situation.

I know how childish this may seem to you but I'm genuinely interested in hearing your opinion and the subject we were discussing is important to me. Anyway I appreciate your help