be talking out of your arse
be talking out of your arseBRITISH, INFORMAL, VERY RUDE
If someone is talking out of their arse, what they say is complete nonsense. Note: `Arse' is a very rude word for a person's bottom. He accused an EU aid official of talking out of his arse. Note: Other words such as backside can be used instead of arse. Much as I appreciate today's team, Dennis is talking out of his backside when he says they're the best ever.