adj

• Not in accord or harmony; conflicting, incompatible.
  "[N]o other kind of liuing beaſtes both behold the fayrenes and the bewtie of the wordle^([sic – meaning worlde]), or is moued with anny reſpect of ſauours, but only for the diuerſity of meates, nother perceaueth the concordaunt and diſcordante diſtaunces of ſoundes, and tunes […]"
• (geology, physical geography, originally US) Of a rock formation or other land feature, or its alignment: cutting across or transverse to neighbouring features.
  "Dikes may be discordant to country rock if they intrude at a high angle to the bedding."
• (geology, physical geography, originally US) Of a rock formation or other land feature, or its alignment: cutting across or transverse to neighbouring features.
• (chiefly genetics) Of two similar subjects, especially twins: differing in some characteristic.

noun

• (chiefly in the plural) A thing which is not in accord or harmony with one or more other things.
  "In the process of dismemberment it must often happen that the true individuality of a soil is lost, so that schemes of laboratory classification sometimes arbitrarily separate agricultural similars and unite agricultural discordants."