Verbal knowledge devoid of substance is fancy or imagination [Iyengar]
Fantasy is the third type of thought pattern that Patanjali identifies, describing it in terms of it being able to be verbalised, but not having a corresponding reality. For instance, I can imagine a green, two-headed monster. I can see it vividly in my mind’s eye, how it looks, how it walks and talks. I can describe it in minute detail, but of course there is no objective green, two-headed monster which I am describing. It is total fantasy, or in Iyengar’s words ‘delusion’.
However, much of what we ‘see’ day to day could be said to be a delusion, in that it may be merely a product of our own imagination, that perhaps there is no objective reality ‘out there’ which we are mapping. How do we know, for instance, that what I see is what you see when we both look at a particular object? Anti-realists might argue that everything is a delusion, as we cannot prove that there is any sort of objective reality beyond what goes on between our ears.
The Buddhist concept of ‘avidya‘ (delusion or ignorance) refers to not seeing things as they are, a slightly different way of framing it. There is no reference to a concept or perception being able to be verbalised, as there is in Patanjali’s sutra.