1.Definition: easy in mind; not worried

"The prisoner seems entirely unconcerned as to the outcome of the examination"

2.Definition: lacking in interest or care or feeling

"The average American...is unconcerned that his or her plight is the result of a complex of personal and economic and governmental actions...beyond the normal citizen's comprehension and control", "Blithely unconcerned about his friend's plight"

3.Definition: not occupied or engaged with

"Readers unconcerned with style"