German

Adjective

gegengleich ‎(not comparable)

1. Diametrically opposed, the mirror image to something else.

   2006, Robin Kerrod, Taschenlexikon Weltraum, translation of original by David Hughes, page 24:

   Materie- und Antimaterieteilchen haben die gleich Masse, ansonsten sind sie gegengleich.

   Matter and antimatter particles have the same mass, but are otherwise exact opposites.

2. Travelling at the same speed in the opposite direction to something else.

Declension

Adverb

gegengleich

1. In a way that is exactly opposed to or the mirror image of another action.