Mom lines

Tan lines from a full bottom swim suit, as opposed to a thong bottom

"Which swim suit are you packing for the beach?"

"Definitely my thong bikini, I don't want mom lines!"

Expiration dating

Engaging in romantic relationships that due to practical circumstance or mutual agreement have a definite end date, yet both partners remain committed to the relationship until that end date.

"Is Kylie still dating that guy she was seeing during study abroad?"

"No, they were just expiration dating. It ended when she moved back home. They sure made the most of their summer together though."