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Webster 1913 Edition

Adj.

Not interesting or affecting; insignificant; not belonging to one.

[Obs.]

Addison.

Adj.

Not interesting; not affecting; not belonging to one. [Not used.]

unconcerning ‎(comparative more unconcerning, superlative most unconcerning)

(obsolete) Not interesting or affecting; insignificant.
(Can we find and add a quotation of Addison to this entry?)