From Longman Dictionary of Contemporary Englishempty nestempty nest (also empty nest syndrome)LEAVE A PLACE a situation in which parents become sad because their children have grown up and moved out of their house → empty
Examples from the Corpus
empty nest• I am swimming away from my friends' deaths, from depression and an empty nest.• Many women enjoy an empty nest.• There will be no empty nest, no shedding of familial responsibilities and expense.• No one ever told me either that a stepmother could suffer so badly from empty nest syndrome. 