8 letters · 11 points in Scrabble
noun one who intrudes or pushes himself forward
noun a small rocket engine that provides the thrust needed to maneuver a spacecraft
originFrom thrust + -er. The surfboard sense was coined (but never trademarked) by Simon Anderson, who created the design in 1980. The name was almost immediately applied generically to any surfboard with that fin design.
Etymology from Wiktionary, CC BY-SA 3.0