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Empty Nest Syndrome. Occurs when a child is about to leave home for the first time and parent begins to realize what it will be like to not have kids around.
Mom: My babies are all growing up!!! :'(
Kid: You're showing signs of ENS
by Darren Higgenbottom August 16, 2012
Erect Nipple Syndrome. Caused by arousal/low temperatures.
"In the freezing cold changing room, it was easy to see she had ENS"
by Goth Pixie December 13, 2003