A prophetic sign functions as evidence where a claim to messengership is present, an extraordinary confirming sign occurs, and opponents are unable to supply a matching counterexample.
Taḥaddī is the challenge to produce a credible equivalent. Muʿāraḍah is a counterperformance or counterexample capable of defeating the particular claim of inimitability.
Merely disagreeing with a prophet is not a successful counterexample. Nor does an unrelated trick, however impressive, answer a challenge framed around a specific sign.