How to search the Latin Vulgate for a word? Is any online website or mobile app or other software ( especially free ) available?
This should meet your requirements:
I use VulSearch (unfortunately currently only for Windows, although since it's open source you could theoretically port it to other OSs). It includes the Douay-Rheims (the English translation par excellence of the Vulgate) so you can search both a strict English translation of the Vulgate or the Latin of the Vulgate itself; or even the Septuagint (although only transliterated Greek).
It also comes with a very useful word search function (for searching Latin or English).
(A feature where you could search for a several-verse-wide range of text with the search parameters would make this tool even more useful in my opinion).
And even a Latin word dictionary.
And of course it's free.
Highly recommend it. I realize this sound like an advert or something but it genuinely is the simplest solution for those who want the Vulgate, along with the meaning of the Latin, in one app. I use it every other day.