pain in the ass is a noun meaning "something or someone that causes trouble; a source of unhappiness". It carries one recorded sense.
something or someone that causes trouble; a source of unhappiness
“washing dishes was a nuisance before we got a dish washer”
“a bit of a bother”
“he's not a friend, he's an infliction”
Definitions, synonyms and semantic relations for pain in the ass come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.