Sensor Saturation
The condition in which a photosite has reached its full-well capacity and can record no additional light.
In depth
Saturation is what clipping physically is, and it happens per photosite and per colour channel — which is why a saturated red flower can clip its red while green and blue still hold detail. Nothing above saturation is recorded, so highlight recovery in processing can only reconstruct from the channels that had not yet saturated.
Examples in practice
A specular reflection on chrome saturates all three channels, leaving pure white with no recoverable structure.