Source : Webster's Revised Unabridged Dictionary (1913)

Aposteme \Ap"os*teme\, n. [L. apostema, Gr. ? the separation of
   corrupt matter into an ulcer, fr. ? to stand off: cf. F.
   apost[`e]me. See {Apostasy}.] (Med.)
   An abscess; a swelling filled with purulent matter. [Written
   corruptly {imposthume}.]