To speak about something that is difficult to convey or too dreadful to be expressed.

ऐसा कुछ कहने के लिए जो व्यक्त करना कठिन हो या जो बहुत भयानक हो।

English Usage: The horrors of the battle were unspeak, leaving the survivors in shock.

Hindi Usage: युद्ध की भयावहताएँ इतनी असाधारण थीं कि जीवित बचे लोग सदमे में थे।