Not identified by name; of unknown name.

नामहीन

English Usage: She received an anonymous tip about the event.

Hindi Usage: उसे घटना के बारे में एक नामहीन टिप मिली।

Something or someone that is unnamed or unknown.

अज्ञात

English Usage: The author of the book remained anonymous.

Hindi Usage: किताब के लेखक अज्ञात रहे।