DuckCorp Dico

Found one definition

1.                 From Japanese-English FreeDict Dictionary ver. 0.1:
                   
   
   
                   
                     
   短呼 /(en)tʃˈaɪniːz(ja)lˈe̞tə (en)tʃˈaɪniːz(ja)lˈe̞tə/, たんこ /tˈäŋko̞/
   (noun (common) (futsuumeishi))
    (noun or participle which takes the aux. verb suru)
   長呼・1 [linguistics terminology] shortening a vowel