A term used to describe metallic filamentary growths, barely visible to the naked eye, that can form on metals and which are stronger than the metal from which they form because of their relative freedom from defects.
Thin hair-like growths on metal that are barely visible to the naked eye, they are stronger than the metals from which they are formed, probably because they are free from defects.
Fine fibrils or crystals from polymers metals etc.