v.1. To change from a frozen solid to a liquid by gradual warming: The lake won't thaw out until the middle of April.
2. To lose stiffness, numbness, or impermeability by being warmed: The skiers gathered around the fireplace to thaw out.
3. To cause something to lose stiffness, numbness, or impermeability by being warmed: The hot sun thawed out the frozen ground. Get another stick of butter from the freezer, and thaw it out in the microwave.
4. To become less formal, aloof, or reserved: The new babysitter looked stern but quickly thawed out after meeting the children.