1.
to be brought under control; to be checked; to be curbed
A worsening trend or negative development is stopped or restrained. Often used in news and formal contexts about economic or social issues.
Usage
歯止め originally refers to a brake or chock used to prevent wheels from moving. The expression 歯止めがかかる describes a negative trend being stopped. The negative form 歯止めがかからない (cannot be stopped) is very common in news reports.