katham -- how; indrah -- Lord Indra; api -- even; kurubhih -- by the Kurus; bhishma-drona-arjuna-adibhih -- Bhishma, Drona, Arjuna and others; adattam -- not given; avarundhita -- would usurp; simha -- by a lion; grastam -- that which has been seized; iva -- as; uranah -- a sheep.

How would even Indra dare usurp anything that Bhishma, Drona, Arjuna or the other Kurus have not given him? It would be like a lamb claiming the lion's kill.