DuckCorp Dico

Found one definition

1.                 From English-日本語 (にほんご) FreeDict+WikDict dictionary ver. 2022.11.18:
                   
   
   
                   
                     
   lumen //ˈlumən// //ˈluːmən// <n>
   1. ルーメン
   SI-unit for luminous flux
   2. 内腔
   anatomy: cavity within tubular organ