/ ˌdaɪəˈmetrɪkl; NAmE / adjective [ usually before noun ]
1.
used to emphasize that people or things are completely different :
He's the diametrical opposite of his brother.
2.
relating to the diameter of sth
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WORD ORIGIN
mid 16th cent. (in sense 2): from Greek diametrikos (from diametros measuring across: see diameter ) + -al .