Another one of those ambiguous questions!
The Shorter Oxford Dictionary defines drawing as:
‘the formation of a line by drawing some tracing instrument from point to point of a surface; representation by lines; delineation as distinguished from painting…the arrangement of lines which determine form.’
‘The term drawing is applied to works that vary greatly in technique. It has been understood in different ways at different times and is difficult to define. During the Renaissance the term ‘disegno’ implied drawing both as a technique to be distinguished from colouring and also as the creative idea made visible in the preliminary sketch.’ 
‘Drawing is the probity of art. To draw does not mean simply to reproduce contours; drawing does not consist merely of line: drawing is also expression, the inner form, the plane, the modeling. See what remains after that.’-Jean-Auguste-Dominique Ingres (1780 – 1867) 
From all I learnt at school in GCSE and A level art, 20 odd years ago, my first response to this question would be that a drawing is an image created using pencil or pen to translate an item or an idea onto paper. When you add colour or paint it becomes a painting- the drawing may still be there underneath, but you have expanded on it. It is fully acceptable to push the boundaries in drawing, more so than when I was at school, but I do think you need a drawing implement to create a drawing.
I don’t see photographs as drawings- a photo is an image captured by a device/piece of equipment. There is art in taking a good photo certainly, but you have not ‘drawn’ it you have captured it. You can edit digital images of that photograph which could be seen as drawing, depending on what you do to it.
I stated previously while looking at the eight artists in part one that I didn’t see Alison Carlier’s spoken drawings as drawings. She is creating a visual image in someone else’s mind but it’s not tangible and no two will be the same. It’s also transient, you will never remember all the details as you did the first time, so each time will be different and after a while the image will fade away and even if you listen again, you won’t create the same image again.. A drawing on paper or canvas you can look at again and again and it will be the same each time. That’s not to say that her spoken drawings are not art- I personally just feel they are not drawings.
These are obviously just my humble opinions. The boundaries of drawing and art are stretched further every day, with new ideas and technologies bringing new ways to create I feel it’s down to your own personal view as to what you see as a drawing, or indeed what you consider art. Art is an extremely personal experience and maybe should not have labels. Is it a drawing or a painting, is it real or imagined, is it art or not, is it good or bad- who’s to say??