What does "critical condition" at the hospital mean?

Life-threatening: Terms such as "critical", "serious", "fair", etc. Are not defined terms in medical jargon, and were probably started by the media. That said, i usually think of "critical" as any patient sick enough to require care in a critical care unit, or icu.

Level of attention: Critical often means a situation that requires constant monitoring, and often has a nurse dedicated to just 1 or 2 such patients as opposed to the standard ratio.