Macabre is an adjective used to refer to something gruesome and horrifying, especially something related to death and dying. It can be pronounced as 'muh-kah-bruh', 'muh-kahb-ber', or 'muh-kahb'.
It comes from the Old French danse Macabré, meaning 'the dance of death'. This in turn is probably a translation of the Latin Chorea Machabæorum, meaning "dance of the Maccabees". The Maccabees were leaders of the Jewish revolt against the Seleucids. The Apocrypha describes the martyrdom of the Maccabees in gruesome detail, but does not speak of dancing. The connection between the Maccabees and dancing remains a minor linguistic mystery, but it is speculated that early plays may have depicted the martyrdom of the Maccabees through dance. On the other hand, it is possible that the Latin Chorea Machabæorum wasn't actually the source of our word macabre, in which case the word is a major linguistic mystery.