Decay/dɪˈkeɪ/ Definition 1 of 5Pro Tip 1/3Progressive Worsening Decay suggests something gradually getting worse, not sudden damage. The building's decay became apparent over the decades. Pro Tip 2/3Negative Connotation Decay implies a loss of value or function, often evoking a sad or negative feeling. The once vibrant neighborhood fell into decay. Pro Tip 3/3Visible Change Decay is often used to describe visible deterioration of objects. Rust and decay marred the old machinery.