Lifeform

In a popular show, the Horta is a silicon-based lifeform.

"We scanned the alien lifeform, and it seems to be silicon-based." "Amazing!"

An interesting lifeform that I like in Larry Niven's sci-fi Known Space is the Bandersnatchi, big slug-like herd animals that were created by the Tnuctipun during the telepathic Thrintun Empire about 1.5 billion years ago.