Oxidised is a term used to describe the process of oxidation, which occurs when oxygen reacts with another substance. Oxidation can cause a variety of changes in the material, including rusting. The two crossword solutions for oxidised are 'RUSTED' and 'RUSTY', both of which refer to the reddish-brown coating that forms on metal surfaces due to oxidation. Rusting is a common form of oxidation and is caused by the reaction of iron and oxygen in the presence of water or moisture.