The phrase "huge milestone" means a significant accomplishment or achievement that is very important and represents a major step forward. Full definition
Starting solid foods is huge milestone in your little ones life and it should be a fun, no - pressure, relaxed experience for them (and you!). (yummymummyclub.ca)
These are long goals that are tracked across all game modes and award Challenge Points for achieving huge milestone goals. (blog.us.playstation.com)
Can't a girl accomplish one huge milestone at a time? (whattoexpect.com)