planetfallEtymologyFrom planet + fall, by analogy with landfall.planetfall means the arrival of a spacecraft on the surface of a planet. Lexicurio rates it Sui generis — a strength score of 91 out of 100.nounThe arrival of a spacecraft on the surface of a planet.““Listen up, grunts. We'll be making planetfall in T-minus three minutes. You'll be joining the war against the Scourge, an alien race of soulless, ruthless automatons.””