Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
2. Lūca or Lūcas, ae, m., Lucanian; v. Lucani, D.
Lūcās, ae, m., = Λουκᾶς, St. Luke, the third evangelist, Vulg. Col. 4, 14; Prud. Apoth. 1002 et saep.