A psychological condition in which a man in his mid to late 50s appears to have lost his mind and drives everyone around him insane with his crabbiness, irrationality, and flash temper. He may exhibit a "blame everyone else" approach when he is in the wrong. He may exhibit opinions that are completely opposite to what he used to have (ie. voting republican when he was a life long democrat or becoming a male chauvenistic pig when he always support women's liberation.)
"Mom, Dad just yelled at me for taking out the garbage. He said I was doing it wrong and got irrationally angry," said the teenaged daughter. "Yeah, he's in Manopause. Nothing he does makes sense anymore," said the mom.