To become accustomed to a new climate or environment. It took him a few weeks to acclimatise to the hot weather in the desert.
To adjust or adapt to a new situation or conditions. She needed time to acclimatise to her new job responsibilities.
To cause (a person, animal, or plant) to become accustomed to a new climate, environment, or set of conditions. Gardeners gradually acclimatise seedlings to cooler temperatures before planting them outdoors.