"El entusiasmo del público fue desbordante" would translate to "The enthusiasm of the public was overwhelming"
If you remove the s you get debordante which is still not French but adding an é makes débordante - yay, a French word :)
Débordante is a feminine adjective and indeed means "that is overflowing", often metaphorically.
Interestingly enough, the construction "es" used to be present in older French (until ca. XVIII century) and then it transformed into "é". There are more of such transformations where a vowel + "s" changed into something else. A well-known one is os->ô like in hospital->hôpital (and the "os" is still visible in "hospitalité")
Instead, think the e sound in “met”.
as the saying goes: remove the "s" to get the Italian word -> debordante.
For those unaware, "desbordante" means overflowing in French (and Spanish). In French, you can pronounce it as "d'eh-boar-daunt". I don't speak Spanish but I think you add an "ay" to the end of it.