In Islamic terminology, something which is makruh (Arabic: مكروه, transliterated: makrooh or makrūh) is a disliked or offensive act (literally "detestable" or "abominable"). It is one of the five categories (al-ahkam al-khamsa) in Islamic law -- wajib/fard (obligatory), Mustahabb/mandub (recommended), mubah (neutral), makruh (disapproved), haram' (forbidden).
Though it is not haram (forbidden) or subject to punishment, a person who abstains from this act will be rewarded.