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Webster 1913 Edition

Adj.

Not relative; without mutual relations; unconnected.

–

Ir-rel′a-tive-ly

adv.

Irrelative chords

(Mus.)

those having no common tone.

–

Irrelative repetition

(Biol.)

the multiplication of parts that serve for a common purpose, but have no mutual dependence or connection.

Owen.

Adj.

[in and relative.] Not relative; unconnected.

Irrelative chords, in music,have no common sound.

irrelative ‎(comparative more irrelative, superlative most irrelative)

Having no relations to each other; unrelated.
Not related to the subject at hand; irrelevant.
- 1934, F Scott Fitzgerald, Tender is the Night:
  When the subject of Mr. Denby fell of its own weight, he essayed other equally irrelative themes, but each time the very deference of Dick's attention seemed to paralyze him, and after a moment's stark pause the conversation that he had interrupted would go on without him.
(music) Describing two or more chords which do not share any notes in common.
Irrelative chords in music are those having no common tone.