To refreeze means to freeze something again after it has already melted or thawed. When you take ice cream out of the freezer, let it soften, then put it back in the freezer, you're refreezing it. When a frozen pizza thaws during transport but gets frozen again at the grocery store, it has been refrozen.

Refreezing matters especially with food safety. When frozen food thaws, bacteria can start growing. If you refreeze it without cooking it first, those bacteria get preserved in the ice, ready to multiply again when the food thaws next time. That's why food packages often warn “Do not refreeze” once thawed.

The word also applies to water in nature. When winter snowmelt refreezes overnight, it can create dangerous ice patches on sidewalks and roads. A puddle that freezes, melts in the afternoon sun, then refreezes at night goes through this cycle repeatedly.

Scientists also study how glaciers and ice sheets melt and refreeze as climate patterns change, since this affects sea levels and weather worldwide.