1. vulgar slang To be very stiff, rigid, or inflexible in one's posture or demeanor. Primarily heard in UK. The guy trundled around the stage so gracelessly and awkwardly, as if he had a poker up his arse. You'd think she has a poker up her arse from the way she sits in class.

2. vulgar slang To be very rigid or inflexible in one's opinions or beliefs. Primarily heard in UK. My grandfather had a real poker up his arse when it came to people living together or having children before marriage.

3. vulgar slang To be irritable, unfriendly, or humorless. Primarily heard in UK. Geez, it was just a joke—you must have a poker up your arse or something. I wouldn't mess around with Mr. Daniels, he's got a poker up his arse today.