diametrically

/ˌdaɪəˈmɛtrɪkəli/

If one thing is the exact opposite of something else, they're diametrically opposed. Here, diametrically is used to mean "totally" or "completely."

Diametrically is an unusual word — it's only used to modify the adjective opposed. When you describe two things that couldn't be more different from each other, you can say they're diametrically opposed. Is your brother a cheerful, optimistic person, while your sister is cranky and gloomy? Then they're diametrically opposed. This word comes from diameter, a line through a circle, in the sense that two points at either end of a diameter are directly opposite each other.

Definitions of diametrically

1. adverb

   as from opposite ends of a diameter
   “when two honest witnesses give accounts of the same event that differ diametrically, how can anyone prove that the evidence you gave was deliberately false?”

   “three of these brushes were approximately 120 feet apart and the fourth diametrically opposite to one of the three”