If you hear someone say their inverter is fitted with anti-islanding protection, it simply means it has islanding detection (often based on voltage and frequency detection) and detects when the grid is down. That way, it stops feeding power back to the grid and protects utility workers.
[pdf] The ability of an inverter to accurately convert DC to AC, operate within specified voltage and current limits, and incorporate safety and control features such as MPPT, transfer switches, and ground fault protec.
[pdf] Safety features like islanding protection automatically disconnect the inverter from the grid to avoid electrical hazards and equipment damage. Efficient operation off-grid requires regular maintenance to maintain peak performance. Understanding these functions secures reliable power during outages.
[pdf] 
