im·pac·tion /ɪmˈpækʃən/
  裝緊,壓緊
  im·pac·tion /ɪmˈpækʃən/ 名詞
  嵌入,嵌塞,阻生(牙科)
  Im·pac·tion n.
  1. Surg. The driving of one fragment of bone into another so that the fragments are not movable upon each other; as, impaction of the skull or of the hip.
  2. An immovable packing; Med., a lodgment of something in a strait or passage of the body; as, impaction of the fetal head in the strait of the pelvis; impaction of food or feces in the intestines of man or beast.
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  impaction
       n 1: the condition of being pressed closely together and firmly
            fixed
       2: a disorder in which feces are impacted in the lower colon
       3: a disorder in which a tooth is so crowded in its socket that
          it cannot erupt normally [syn: impacted tooth]
       4: a sharp collision produced by striking or dashing against
          something [syn: impingement]