hurtful, harmful, pernicious
Derived from the active participle of the verb أَضَرَّ (ʔaḍarra, “to harm, to injure”), from the root ض ر ر (ḍ r r); compare ضَرَّ (ḍarra, “to damage”).
Practice speaking and memorizing "مضر" and many other words and sentences in Arabic.