The Collaborative International Dictionary of English v.0.48:

Inofficious \In`of*fi"cious\, a. [L. inofficiosus: cf. F.
   inofficieux. See In- not, and Officious.]
   1. Indifferent to obligation or duty. [Obs.]
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            Thou drown'st thyself in inofficious sleep. --B.
                                                  Jonson.
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   2. Not officious; not civil or attentive. [Obs.] --Jonhson.
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   3. (Law) Regardless of natural obligation; contrary to
      natural duty; unkind; -- commonly said of a testament made
      without regard to natural obligation, or by which a child
      is unjustly deprived of inheritance. "The inofficious
      testament." --Blackstone. "An inofficious disposition of
      his fortune." --Paley.
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Bouvier's Law Dictionary, Revised 6th Ed (1856):

INOFFICIOUS, civil law. This word is frequently used with others; as,
inofficious testament, inofficiosum testamentum; inofficious gift, donatio
inofficiosa. An inofficious testament is one not made according to the rules
of piety; that is, one made by which the testator has unlawfully omitted or
disinherited one of his heirs. Such a disposition is void by the Roman civil
law. Dig. 5, 2, 5; see Code, 3, 29; Nov. 115; Ayl. Pand. 405; Civil Code of
Lo. art. 3522, n. 21.