DROWN stands for Decrypting RSA with Obsolete and Weakened eNcryption. DROWN is another downgrade attack over SSL hence this time over SSLv2.
SSL has a good history with downgrade attacks likewise Lucky13, Crime, BEAST, Poodle. Currently %33 of internet servers uses SSLv2. With DROWN an attacker can decrypt connection with server which has SSLv2 enabled.