Untraceable means impossible to follow back to its source. An untraceable call, untraceable funds, effectively untraceable.
Very little is truly untraceable, which is why the word usually means too expensive to trace rather than impossible. Cash is the ordinary example, and it is why serious crime still runs on it.
1adjectiveuntraceableImpossible to follow back to its source.
“The kidnappers used an untraceable phone to make their demands.”
untraceable is a quality.
From un- + traceable.
Etymology from Wiktionary, CC BY-SA