What it means
To go feral is to lose the last scraps of chill and turn gloriously wild for a minute. It's used for people losing it from hype, hunger, obsession, or pure chaos, with clawed-up energy that feels half goblin, half ecstatic.
Usage examples
"The crowd went feral when the band walked out."
"I go feral every time they drop a new episode."
"She saw the limited drop go live and went feral in the group chat."
"Don't put chips on the table before everyone's eaten, mate, people go feral."
Where it comes from
It comes from feral, the standard English word for an animal that's gone wild after living domesticated. From there it got playfully stretched to people, especially online, for moments when someone drops the civilised mask and acts delightfully unrestrained.