"Knocked for loop" is an idiomatic phrase used to describe a state of confusion, shock or surprise. The term is often used to describe someone who is caught off guard or surprised by a situation. Antonyms for the term can include "prepared," "alert," "ready," "in the know," or "unaffected." These words suggest a state of awareness and readiness for potential situations, rather than being caught off guard. Additionally, "composed," "unperturbed," "unbothered," and "poised" could be used as antonyms, implying a sense of calm, collectedness, and control in the face of unexpected or difficult circumstances.