A lack of meaning in personal existence.

Existential vacuum is a term coined by Viktor E. Frankl, concentration camp survivor, and author of the book, "Man's Search for Meaning".

"The existential vacuum manifests itself mainly in a state of boredom... ....for instance, "Sunday Neurosis", the kind of depression which afflicts people who become aware of the lack of content in their lives when the rush of the busy week is over and the void within themselves becomes manifest." - Viktor E. Frankl, in "Man's Search for Meaning"