Subjective experience is the awareness of an internal representation.

What is awareness then? Do you see my point? Either you end up with a circle of references or an infinite regress of definitions to describe the ineffable.

It’s the problem of qualia [1]. They can’t really be defined, only pointed at. My experience of seeing the colour red is non-universalizable. Thus the word red can only point at it, it can’t describe or define it.

[1] https://en.wikipedia.org/wiki/Qualia