> A drop in the level of the uterus during the last weeks of pregnancy as the head of the fetus engages in the pelvis.
The word lightening can also mean 1) to make something lighter or 2) the transfer of crude oil to a relatively larger tanker from a smaller in order to enter a port.
Funny aside: I looked up the word “lightening” to ensure it wasn’t an alternate spelling or something. It’s not. Instead, it means:
> A drop in the level of the uterus during the last weeks of pregnancy as the head of the fetus engages in the pelvis.