aer·o·gel 
(ârə-jĕl′)
(ârə-jĕl′)n.
A highly porous solid formed from a gel, such as silica gel, in which the liquid is replaced with a gas.
- running noose
- running start
- running stitch
- runny
- Runnymede
- run off
- runoff
- run off at the mouth
- run off with
- run-of-the-mill
- run on
- run-on
- run (one's) eyes over
- run one's eyes over
- run-on sentence
- run out
- runout
- run out of
- run out of gas
- run out of gas/steam
- run out of steam
- run out on
- run over
- run rings around
- run run out the clock