Which term is used to describe a blood pressure of 90 mm hg systolic and 50 mm hg diastolic?

Hypotensive

Explanation:

Blood pressure is considered low (hypotension) when the measured value is less than 90 systolic or 60 diastolic. Some people use a mean arterial pressure (MAP) of <65 to define hypotension.

In this case the diastolic pressure is in the hypotensive range and the systolic is borderline. The MAP is 63.