Milestone

n.	1.	A stone serving the same purpose as a milepost.
	2.	An event or accomplishment marking a significant advance in an endeavor; a notable achievment; as, putting a man in orbit was a major milestone on the way to the moon.

Noun	1.	milestone - stone post at side of a road to show distances Synonyms: milepost
	2.	milestone - a significant event in your life (or in a project)

bench mark, bookmark, cairn, cardinal point, catstone, chief thing, climax, core, cornerstone, crisis, critical point, crux, essence, essential, essential matter, fundamental, gist, gravamen, great point, heart, high point, important thing, issue, kernel, keystone, landmark, lighthouse, lightship, main point, main thing, mark, marker, material point, meat, menhir, milepost, monument, nub, occasion, pharos, pith, pivot, platform, real issue, salient point, seamark, sine qua non, substance, substantive point, the bottom line, the point, tower, turning point, watchtower