1) In Islam, a forbidden activity, food, drink, or thought. Examples of haram things are: eating pork, drinking alcohol, having sex at daytime during Ramadan
, extramarital sex, neglect of prayer and fasting, and blasphemy.
2) In the slang of Arabic and languages influenced by Arabic, anything evil or sinful. Forms compounds like Arabic ibn haram 'bastard' (lit. 'son of sin'), and Malay anak haram (also meaning 'bastard').
Uh, isn't making out in a mosque kind of a haram activity? I don't think it matters if you're married.