approacher

noun

Etymology: From approach + -er.

1. Someone or something that approaches.

   “The monkeys’ calls warn other animals of approachers.”

   “1589, Paul Ive (translator), Instructions for the Warres by Raimond Beccarie de Pavie, Seigneur de Fourquevaux, London: Thomas Man and Toby Cooke, Chapter 5, p. 38, […] houses or other thing standing néere vnto a towne, or fort, are meanes to surprise and approach vnto it, and the approacher not be discouered, or impeached by the defenders.”

2. An asteroid on a near-Earth trajectory.

   “Extensive upgrades to the Arecibo antenna will be completed this spring, providing dozens of Toutatis-quality detections per year, spacecraft-quality images of the closest approachers, and hundred-pixel images of dozens of main-belt asteroids ( 9 ).”

   “We have some close approachers," he says, "but not one that would have an impact trajectory."”