The Dow shed just over one percent, while the S&P 500 dropped about one-and-a-half percent and the Nasdaq plunged nearly 1.6%.

All three ended the session at their lowest closing levels in well over three months.

Adding to investor anxiety was the potential of a partial U.S. government shutdown by the weekend - and a whole lot more, says Shana Orczyk Sissel, Founder and CEO of Banrion Capital Management.

"We have the Amazon antitrust suit that is driving down a lot of the bigger tech names, including Apple, Google, and the like. And I think people are starting to feel a little defensive. Consumers are feeling a little stretched. And we have a bunch of strikes going on in a potential government shutdown. So there's a lot of risk in the market right now."

Amazon shares ended 4% lower after the U.S. Federal Trade Commission filed a long-awaited antitrust lawsuit against the online retailer.

In other notable moves, shares of Immunovant surged 97% after early-stage data from the drug developer's experimental antibody treatment exceeded analysts' expectations.

This week brings lots of economic data, including the latest view on inflation with Friday's personal consumption expenditures price index. Second-quarter GDP figures and remarks by Fed Chair Jerome Powell are also on tap.