Now, a good consonant definition, in term of pronunciation, is that with consonants, the articulators either touch or they come are very, very close to one another.
Now, we do have 3 consonants that don't follow that rule exactly, in fact, they don't touch, the articulators don't touch with these three consonants, instead the articulators approximate with one another.
So, in answer to your question, 'what is a vowel', well, a good definition is that vowels are made with the articulators holding a shape but not actually touching.
Well, a good definition of consonance sounds is that it is a sound whereby the articulators either touch or almost touch and then releasing suddenly or slowly or they hold their position.
And with the OO vowel sound, as in 'who', 'shoe' and 'move', the lips are rounded and the back of the tongue is high but again, nothing actually touches, it just, the articulators just hold a shape.