A milestone == a mile marker. That is where the term came from. https://en.m.wikipedia.org/wiki/Milestone https://en.m.wikipedia.org/wiki/Milestone I think th

A milestone == a mile marker. That is where the term came from. https://en.m.wikipedia.org/wiki/Milestone https://en.m.wikipedia.org/wiki/Milestone I think the term is rather unimportant. You could also use the term epic.