I (and I think this is a pretty popular perception) consider a "full stack" developer as someone who has thoroughly mastered at least 1, and is familiar with at least 1 or two other approaches from each layer in the following list:
Web Layer: Javascript (and/or one of its many frameworks like jQuery, Backbone, etc), Ruby, etc.
Server Layer: Django, Rails, Cake, Node, etc.
Data Layer: Postgres, SQL Server, etc.
All of that stuff you can learn for free on-line. Come up with an idea for a website that involves storing and manipulating data and can handle large numbers of people using it simultaeously. If you can make the whole thing by yourself, you are a full-stack developer. If you can't, figure out what the missing piece is and learn it.
Web Layer: Javascript (and/or one of its many frameworks like jQuery, Backbone, etc), Ruby, etc. Server Layer: Django, Rails, Cake, Node, etc. Data Layer: Postgres, SQL Server, etc.
All of that stuff you can learn for free on-line. Come up with an idea for a website that involves storing and manipulating data and can handle large numbers of people using it simultaeously. If you can make the whole thing by yourself, you are a full-stack developer. If you can't, figure out what the missing piece is and learn it.