below the normal; less than or inferior to the normal: a subnormal amount of rain.

What is subnormal abnormality?

is that abnormal is not conforming to rule or system; deviating from the usual or normal type while subnormal is less than normal.

Is correctly a real word?

To do something correctly is to to it accurately: to do it right. A correctly spelled word is spelled right. When something is correct, it is right or accurate.