silica aerogel

noun

: colloidal silica in the form of a fine lightweight powder with grains having minute pores that is made from silica gel and used chiefly as thermal insulation especially at low temperatures (as in refrigerators)

Love words?

You must — there are over 200,000 words in our free online dictionary, but you are looking for one that’s only in the Merriam-Webster Unabridged Dictionary.

Start your free trial today and get unlimited access to America's largest dictionary, with:

• More than 250,000 words that aren't in our free dictionary
• Expanded definitions, etymologies, and usage notes
• Advanced search features
• Ad free!