说胡话 is the most common collocation. It can mean delirious rambling (when sick) or just talking rubbish. Similar to 胡说 and 胡说八道.
history
胡 originally referred to northern nomadic peoples. Over time it acquired a sense of 'reckless, wild, random' - hence 胡话 (wild talk), 胡来 (act recklessly), 胡闹 (make trouble).
