Patients may talk deliriously when they have a fever.
Tips
grammar
胡言乱语 follows the ABCB pattern where A and C are adverbs (胡/乱 = recklessly/chaotically) modifying B and D (言/语 = speech). Similar idioms: 胡说八道 (talk rubbish), 胡搅蛮缠 (pester unreasonably).