To adapt to a new environment, often by limiting exposure to the new environment, then increasing it over time. Examples of acclimate would include
1) introducing new fish to a pond, typically accomplished by first floating the still-closed bag to stabilize the water temperatures, then gradually introducing pond water into the bag, culminating in allowing the fish to exit the bag.
2) hardening off seedlings by placing them in a sheltered spot for a few hours each day, gradually increasing the amount of time they are outdoors. This ensures sturdier plants, capable of withstanding outdoor conditions including wind and sun exposure.