The definition of stepped up is something that has been increased or is more intense.(adjective)
An example of stepped up is when someone increased his efforts to pass a test.
Stepped up is defined as took responsibility or did what was right.(verb)
An example of stepped up is when a company admitted that the product it made wasn't safe, voluntarily recalled it and compensated everyone for what had happened.
See stepped-up in Webster's New World College Dictionary
See stepped-up in American Heritage Dictionary 4
Learn more about stepped-up