Lewis & Short

ăb-ŏrĭor, ortus, 4, v. n. dep.

  1. I. (Opp. of orior.) To set, disappear, pass away (very rare): infimus aër, ubi omnia oriuntur, ubi aboriuntur, Varr. L.L. 5, 7, § 66 Müll.
    Of the voice, to fail, stop: infringi linguam vocemque aboriri, Lucr. 3, 155.
  2. II. Of untimely birth, to miscarry (v. ab, III. 1.); Varr. ap. Non. 71, 27; Plin. 8, 51, 77, § 205.