What does it mean if a patent application has a status of “rejected”?

A nonprovisional patent application is designated as “rejected” if, during prosecution before allowance, it contains an examiner’s action that has not been replied to by the applicant. As stated in MPEP 203.02:

A nonprovisional application which, during its prosecution in the examining group and before allowance, contains an unanswered examiner’s action is designated as a “rejected” application. Its status as a “rejected” application continues as such until acted upon by the applicant in reply to the examiner’s action (within the allotted reply period), or until it becomes abandoned.