The phrase "casts loose" implies an action of releasing or freeing something or someone. Antonyms for this phrase would, therefore, be words that mean the opposite- restraining, tightening, or keeping in place. Examples of antonyms for "casts loose" could include "fastens," "safeguards," "secures," "ties," "buckles," or "clamps." These words denote actions that create constraints and boundaries, preventing things from moving or slipping away. While "casts loose" represents the idea of liberation and freedom, antonyms like "fastens" and "secures" imply protection and stability. The choice of words will depend on the context, and using antonyms can help convey a completely different meaning or tone in a sentence.