Answer: It is wishing that the blessing of others would cease to exist or hating to see others enjoy a blessing.

Allah Almighty says: {And from the harm of the envier when he envies.}

Anas ibn Mālik (may Allah be pleased with him) reported that the Prophet (may Allah's peace and blessings be upon him) said: "Do not hate one another, do not envy one another, and do not turn your backs on one another, but be, O servants of Allah, as brothers." [Narrated by Al-Bukhāri and Muslim]