A Tuned Mass Damper (TMD) is a device installed in structures such as buildings or bridges to reduce unwanted vibrations caused by wind, earthquakes, or other forces. It consists of a mass mounted on springs and dampers, tuned to move out of phase with the structure's oscillations. By doing so, it absorbs and dissipates vibrational energy, stabilizing the structure and preventing damage or discomfort. While not directly a cybersecurity concept, the term may appear in discussions about physical security of critical infrastructure, where maintaining structural integrity is essential for protecting sensitive equipment and data.