What is the Blood? The Blood is blood in which the spark, the flame, the virtue (call it what you will) has been awakened.
What is a Witch? Someone of the Blood who has the Sight.
What is the Sight? Being able to sense/see/understand Unseen things, things and connections that normally can't be sensed via the vehicle of the five senses (hence sometimes being called a Sixth Sense).
What is a Witch? Someone of the Blood who has the Sight and has connections (usually via spirit familiars, totems, or the Fey/fetch relationship or all of the above) with the Otherworld, the land of Faery, the Unseen realm.
Can you be a Witch and not have any of these? Ah, that is the question...