rusting

1. gerundparticiplepresentpresent participle and gerund of rust

plural rustings

1. The development of rust on a surface.

   An example will best make the matter clear, and throw light, perhaps, on many cases of apparently mysterious rustings.

   1899, Scientific American, volume 81, page 309

2. The phenomenon where the fur of a black cat develops a brown colour when exposed to sunlight.