What does the dashboard light with an exclamation point inside a half circle on Chrysler 300 mean?

That's the Electronic Stability Control (ESC) / Traction Control System (TCS) warning light. The exclamation point in a circle (sometimes a half-circle, depending on the vehicle's year and model) indicates a problem with one or both of these systems.

This means your car's systems that help maintain control during slippery conditions or prevent loss of traction are either malfunctioning or have been turned off. You should have your Chrysler 300 inspected by a mechanic as soon as possible to diagnose and fix the underlying issue. Driving with this light illuminated reduces your car's safety and stability.