Underprop means to support or reinforce, usually in the context of buildings or structures. Antonyms for this word include weaken, exhaust, damage, demolish, and collapse. Weaken means to make something weaker or less strong, which is the opposite of underprop, where something is made stronger. Exhaust means to deplete or drain energy or resources, while underprop ensures that the energy and resources are maintained. Damage means to harm or cause injury, while underprop aims to protect and preserve. Demolish means to tear down or destroy a structure, which is the opposite of underprop, where the aim is to keep it intact. Collapse means to fall down or give way, while underprop ensures that the structure remains upright and stable.