وَ«يَا لَكَاعِ» بِمَعْنَى لَاكِعَةٍ
Translation: 'O base woman!', with «لَكَاعِ» corresponding to «لَاكِعَةٍ».
It is a feminine epithet used in address, not an imperative verb-noun here.
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Lakāʿi as a Feminine Address
Asmāʾ al-Afʿāl — Definition, Uses and Parsing
وَ«يَا لَكَاعِ» بِمَعْنَى لَاكِعَةٍ
Translation: 'O base woman!', with «لَكَاعِ» corresponding to «لَاكِعَةٍ».
It is a feminine epithet used in address, not an imperative verb-noun here.