The end result is the same. Usually, we use "defrosting" in the context of an oven or microwave, that is, thawing by artificial means. "Thawing" is usually leaving something frozen out in natural ambient air, or moving the frozen food from the freezer to refridgerator.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.
soheil1unfreezeTo my knowledge that is only used in context of your computer freezing up, or in economics contexts.