Any of a large class of siloxanes that are unusually stable over a wide range of temperatures; used in lubricants and adhesives and coatings and synthetic rubber and electrical insulation WordNet 3.0 & Open English WordNet

In organosilicon and polymer chemistry, a silicone or polysiloxane is a polymer composed of repeating units of siloxane. Wikipedia

Class of liquid or rubbery, heat-resistant, stable substance consisting of polymers or oligomers of siloxane with other atoms Wikidata

Any of a class of inert, semi-inorganic polymeric compounds (polysiloxanes), that have a wide range of thermal stability and extreme water repellence, used in a very wide range of industrial applications, and in prosthetic replacements for body parts. Wiktionary

Any of a class of inert compounds of silicon. Wiktionary (translation)