British & Australian informal to spoil something or do something badly
He was messing with the central heating and I think he's gone and buggered it up.
bugger up
verb to spoil something; to ruin something; to exhaust something UK, 1937
phrasebugger up bugger up sth • bugger sth upBrE informal to spoil something or do it very badly: I really buggered up the first exam.Don't give it to Emma. She'll only bugger it up.■ SIMILAR TO: mess up, cock up BrE informal