• (adv.) In a diametrical manner; directly; as, diametrically opposite.
Di·am'e·tric·al·ly adverb In a diametrical manner; directly; as, diametrically opposite. « Whose principles were diametrically opposed to his.» Macaulay. 
[adv] - as from opposite ends of a diameter
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 apar...
[Literary terms] as from opposite ends of a diameter