Without the definite article the, are you not allowed to use the word TV as an abstract noun, as in what's on TV?
Or even with the definite article the, can it still mean abstract noun TV?

Question

Without the definite article the, are you not allowed to use the word TV as an abstract noun, as in what's  on TV?
Or even with the definite article the, can it still mean abstract noun TV?

Answer

If you have an example sentence using the word "the" while speaking about TV abstractly, you could get some more specific feedback :) I just couldn't think of any

Answer

I can't think of any examples where I'd use "the" when referring to TV abstractly, off the top of my head.
- Do you like TV?
- What's on TV tonight?
- Kids watch TV a lot.
- I used to watch TV only on the weekends.
- Everyone watches TV once in a while.

Sometimes using "the" changes the meaning, like "Do you like TV?" vs "Do you like the TV?"

I think you could say "the" in these sentences, and it would sound awkward to me but I would understand it. "Kids watch the TV a lot," if used in a context where it's obvious that you're talking about TV abstractly, would be understandable. It just doesn't sound very natural. I don't know if it's technically grammatically incorrect or not, I'm just speaking from experience as a native English speaker.

Answer

In the particular question, 
'What's on TV' is correct if you mean in context to some program.
However, 'when you say what's on the TV?', it has the meaning of 'What physical thing is present or placed on the television'. 
I hope this cleared your confusion.

Answer

Could you please tell me your question clearly?

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