But Austrians and Keynesians aren't diametrical in the same way.
From the economist.com
We believe that there is a third way wedged in the nomansland between the diametrical opposites.
From the en.wikipedia.org
Laura Heisler is memorably funny and sympathetic as Helena, Anna's best friend and diametrical opposite.
From the thenewstribune.com
He settled on Sidibe after realizing that she was the diametrical opposite of her on-screen character.
From the independent.co.uk
I'm not sure the establishment Republicans and the tea party aren't as diametrical as either is with Democrats.
From the economist.com
Some protested the honor, saying Obama's support of abortion rights puts him in diametrical opposition to Catholic teachings.
From the thestate.com
The second, almost diametrical, reality is that the Giants, at 9-5, still are mathematically in very good position to make the playoffs.
From the newsday.com
Apparently, the term is used so loosely in the UK and the continent that it has come to mean the diametrical opposite of its intended meaning.
From the economist.com
As long as he was handpicking his successor, you'd think Jobs would have chosen someone in his own image, but he and Cook, who was Jobs'COO at Apple, are in a lot of ways diametrical opposites.
From the poy.time.com
More examples
Diametral: related to or along a diameter; "the diametral plane"
Diametric: characterized by opposite extremes; completely opposed; "in diametric contradiction to his claims"; "diametrical (or opposite) points of view"; "opposite meanings"; "extreme and indefensible polar positions"
(diametrically) 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? ...
Of or pertaining to a diagonal; Completely opposed