ex·ten·sor /ɪkˈstɛn(t)sɚ/
  伸肌
  ex·ten·sor /ɪkˈstɛn(t)sɚ, sɔ(ə)r/ 名詞
  (拉)伸肌
  Ex·ten·sor n.  Anat. A muscle which serves to extend or straighten any part of the body, as an arm or a finger; -- opposed to flexor.
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  extensor
       n : a skeletal muscle whose contraction extends or stretches a
           body part [syn: extensor muscle] [ant: flexor muscle]