Frost-bound refers to being frozen, stuck, or immobilized due to extreme cold weather conditions. Its antonyms, therefore, are the opposite of these meanings. These could include "thawed," "unfrozen," "unstuck," and "mobile." Thawed means that something has melted or has become unfrozen due to the warmth of the sun or another source of heat. Unfrozen means that something is free from being frozen, and thus, can move without any hindrance. Meanwhile, unstuck means that something is no longer stuck or affixed to another object or surface. Lastly, mobile means that something is capable of moving or traveling easily, without any restriction or impediment.