What does the term 'Grand Design' refer to when describing spiral arm texture?

Answer

Arms that are smooth, well-defined, and extend nearly all the way from the center to the edge

'Grand Design' describes a smooth, highly organized spiral structure where the arms are clearly defined and span the majority of the galactic disk radius.

What does the term 'Grand Design' refer to when describing spiral arm texture?
Spaceclassificationgalaxyastronomy