A swamp slug
A slug was a kind of slowly moving gastropod organism. Several varieties of slugs existed, including sea-slugs, sand slugs, brain slugs, and also swamp slugs. The silicon-based entities known as Exogorths were also referred to by the name "space slug."
After outmaneuvering them with his freighter, the Millennium Falcon, in terms of speed, the smuggler Han Solo once drew a comparison between Imperial-class Star Destroyers and slugs.