Translation:Αυτό το λιοντάρι.
Λέοντας is an old-fashioned way of saying λιοντάρι. The actual ancient greek word for this animal is Λέων. These 2 forms survive only in scientific texts or in a really formal context of speaking, and are also used for the creation of some compound words (eg. Λέαινα = Lioness).The only everyday modern use I can think of Λέων/Λέοντας is for the name of the astrological sign of Leo.