Dea Foeda refers to the personification of lust and betrayal, particularly in the context of Dido's passionate love for Aeneas in Vergil's 'Aeneid'. This term embodies the destructive nature of uncontrolled desire and how it leads to moral decay and shame, ultimately influencing the fate of characters in the epic. The representation of Dido as the Dea Foeda highlights the conflict between duty and passion, a central theme in Aeneas's journey.