The primary meaning of cursing is expulsion from mercy, to be ostracised, and the infliction of God’s anger. If a Muslim curses someone who doesn’t deserve it. The curse will come back to haunt him both here and in the Hereafter.
The author of Lisaan al-‘Arab [a Famous Arabic-language dictionary – Translator] said: La’n (curse) means being cast out far from goodness, and it was said that it means being cast away far from Allaah, and from people.
If you curse, you use very impolite or offensive language, usually because you are angry about something.