No, I am not upset and spouting foul names about the tile guy or something.
Bullnose is a new term in my vocabulary (extensive? not so much). It is when the edges of a tile are rounded off for a curved edge instead of the flat sharp edge tile comes with.
It makes a wonderful transition up against a wall.
Or in this case used as a transition from the carpet of the bedroom over the threshold into the bathroom.
Here you can see the bullnose being used as the edges of the tub surround.