What does it mean to say that the man is rh?

Male Rh positive usually means Rh blood group positive.

Rh blood group is one of the earliest blood group systems found in Indian rhesus monkeys. This system is different from ABO blood group system, only negative and positive. Rh blood group system contains five antigens: big C, small C, big D, big E and small E. Human red blood cells containing D antigen are called Rh positive, otherwise they are negative.

RH positive blood group accounts for 99.7% of Han nationality and most ethnic groups in China, accounting for about 90% of minority individuals, while Rh negative blood group accounts for only 3‰. Rh positive only represents the antibody types of most people in the Rh blood group system.