What can 달 mean besides "moon" and "month"?

 ANSWER: the month a woman is expected to give birth (해산할 달)

"Expecting Mother," by Gerry Bevers

When the moon is full at night,

It is big, round, and quite bright.

When a belly's full and tight,

A child's ready for the light.

달 can mean either "moon" or "month," and 차다 means "to be full," so 달이 찼다 can translate as "The moon is full." But when a woman is ready to give birth, her belly looks almost as big and round as a full moon, so when one is referring to a pregnant woman, 달이 찼다 would translate as "It's time [for the woman] to give birth."

By the way, 미국에서는 달빛이 (moonshine) 불법이다.

From Dong-A's Prime Korean-English Dictionary