Yes, sessile. I first encountered this word in the science fiction works of Larry Niven. Niven came up with some really great aliens. I've mentioned the Kzinti here before.
One of them was the Grog. A sessile alien, the Grog just sits on a rock using its weak mental telepathy to command bypassing rats and toads (or whatever that distant desert planet has that is similar) to hop into its mouth.I guess the cell phone networks aren't very good on its planet, and they haven't opened Pizza Hut delivery there yet.
In its younger stage of life, before it sits on a rock and never moves again, the Grog resembles a Yorkshire terrier. Probably a lot cuter than the long-tongued muppet cones they grow into. But I am not sure if anyone wants a pet Yorkie that is telepathic.
Grogs are a remnant of a vast interstellar empire that controlled the galaxy millions of years ago, in Niven's stories. Called the Slavers (or Thrintun, see this detailed page), they used their telepathic prowess to mentally enslave any race they came across. I guess they were a bunch of lazy SOB's. After their interstellar wars and efforts to put down rebellions (including kevorking the galaxy), they settled down, devolved and degenerated, and sat still, using their abilities to get the food to their mouths so they didn't have to go anywhere.
Sort of like those guys in the sitcom "Friends" who never left their recliners. TV remote in one hand, smart phone used to order pizza in the other.
Time to get up and do something. Either that, or officially name my chair after Kublai Khan.