And as on Tuesday it was again France's Tessa Worley who chased the 21-year-old home in poor visibility.
Shiffrin claimed her 25th World Cup triumph but only her third in giant slalom by clocking a time of 2min 09.40sec with Worley 0.15sec adrift and Germany's Viktoria Rebensburg in third at 0.18.
Worley did enough to retain her position at the top of the World Cup giant slalom standings with Shiffrin cementing her leading position in the race for the Crystal Globe.
"It was a big fight," said Shiffrin. "There was so much snow coming down, I could feel my skis in the track speeding up, and then coming out slowing down. And I was like 'oh, this isn't good, it's got to be slow'. So I kept fighting and fighting.
"It's two victories, but in the same place. It would be nice to repeat it at a new venue, but it's definitely nice to feel like I can ski free for four runs in a row."
Before Semmering, Shiffrin's only previous giant slalom success had come at another Austrian ski resort at Solden in October 2014.
The Olympic champion will be favourite to complete a superb week in Thursday's slalom, also at Semmering.
Shiffrin will be gunning for her 26th World Cup victory in the slalom, including her seventh-straight win in the specialist event – one shy of the record eight-race slalom win streak held by Switzerland's Vreni Schneider and Croatia's Janica Kostelic.
"I'm not looking at the records," Shiffrin said. "I'm just happy to have another giant slalom win.
"Two days ago I was wondering if I would ever win a GS again, and now I have three wins, so that is a really special feeling that I have."
