Wiktionary
zulm
n. (context Islam English) sin, wrong-doing, injustice
Wikipedia
Zulm
Zulm is the Arabic word used interchangeably for cruelty or unjust acts of exploitation, oppression, and wrongdoing, whereby a person either deprives others of their rights or does not fulfill his obligations towards them. In Turkish, it is known as zulüm.
People who commit zulm are called zalim-een.
In the Islamic context injustice or acts of cruelty are attributed to human acts and not to Allah: God does not do injustice to anyone. It is the people who do injustice to themselves.