J.S.
Oh, I noticed. My babies somersaulted hard enough to make me throw up and then engaged in my pelvis. With my eldest daughter, she did it hard enough to also pop my mucus plug at the same time.
"Dropping" or "lightening" simply refers to when the baby is not only head down, but stays head down and engages its head firmly in the pelvis and isn't floating freely in amniotic fluid any longer.