What is the meaning of Isto?

A professional, a person who belongs to a profession.

this

ablative masculine/neuter singular of iste

this (the thing here)

this (the thing being discussed; the current situation)

this (the thing here)

this (the thing being discussed; the current situation)

this sentence, this word, this dictum

that’s right, that’s correct; akin to English this!

yeah! (expresses happiness with an outcome)

neuter nominative/accusative/vocative singular of isti

as well, also, too, likewise

Source: wiktionary.org