And in PT-BR it means winning by a big difference.
The usages I have found in English seem to mean this too. Additionally, there are strong indications that most of the people who use this expression are Brazilian:
Human-Genocide: I still see a BIG "we can't do it" in the eyes of Asian and African teams with big teams coming to this like if it's a shore and worth nothing, making them lose by 5 or 6 rather than a competitive 2 - 0.
Annotator: It's quite rare to see any Asian or African side losing by an elastic score.
Match Thread: Guangzhou Evergrande vs Atletico Mineiro (Club World Cup 3rd place playoff)
For that example, /u/Annotator's profile implies that they are Brazilian (because they say "in Brazil" as if they live there).
In this example, there's a pretty clear connection with Portuguese (from context, it's likely Brazilian Portuguese), since that's what the rest of the page uses:
Nicknamed The Glorious applied by knockouts in the early twentieth century , the football team is responsible for more elastic score in the history of Brazilian football : 24x0 Sport Club on the hose .
BOTAFOGO FR - Ninguém Cala o Nosso Amor!!
This all points to "elastic score" being a literal translation of the (Brazilian) Portuguese idiom. But it's not idiomatic in English.
It's far more idiomatic to call this a blowout instead.