I just posted this in a similiar thread in the general forum. For me, i'm stuck at "really sharp", but it goes something like this
Dull == doesnt cut an arm hair or tomato.
Sharp == can shave arm hair or cut a tomato with some downward pressure and sawing
Really Sharp == can whittle a strand of hair under tension, or fall through a tomato with just a slight draw stroke
Scary sharp == can whittle a free standing strand of hair, or falls through a tomato on its own with just the blade weight
Holy Crap Sharp == touch and bleed; no pain like getting cut by a shard of glass.