I'm pretty sure I took the definitions below from a previous thread of this nature - if you search on one of the phrases you should find it.
Junior tester - Can read test cases and execute them; can raise good fault reports
Tester - Can design tests using basic test techniques; is capable of active participation in documentation reviews; reviews fellow tester's tests; capable of automating tests
Senior tester - Can design tests using advanced test techniques; is capable of active participation in technical reviews; can produce test plans; may specialise in one or more area (e.g. Performance testing); mentors more junior testers; able to communicate with customers; implements test improvements
Test Lead - Can produce test strategies; capable of man-management; influences test improvement; understands and produces metrics;
Test Manager - As Test Lead but on bigger project or more projects