Examples of use of hardening
1. "That shows they‘re hardening" immigration enforcement.
2. The bad feelings have been hardening for several years.
3. "When you think about hardening a tunnel, you can‘t just go into Home Depot and buy a tunnel–hardening kit," Schiliro said.
4. Opinion is hardening that David Cameron is too little tested.
5. That mood has been hardening because of the domestic situation.