A scunder can be a person or a thing. It means a "nuisance". It can be found with several pronunciations. Scunner, Scundered, Scunnered, Scunnert. It is commonly used in ulster (Northern Ireland), Scotland and the North of England.
Joe is a scunder. (Joe is a pain / nuisance)
I am scundered today (I am fed up today)
This job scunders me. (This job bores /sickens / depresses me)