Irish slang used by scumbags for someone they consider morally lower than a scumbag, typically a paedophile or murderer.

A woman of ill repute. A promiscuous female. A dirty, venerial whore who men should not touch with the longest of bargepoles.

Someone who doesn't wash that often. (Northern Irish slang)

small, possibly stupid birds that sleep in the dirt during the darkest of hours. When approached on bike, the elusive dirtbird will frantically fly in the face of the on-comer. A defense mechanism? Or perhaps another cruel joke by Mother Nature...