When bad things appear to happen in large quantities. Usually used as a substitute for an expletive (e.g. shit) as a exclamation of how bad a situation might be.
'Bucket loads' of 'crap' = crapbuckets.
"Crapbuckets, I've got my first exam tomorrow and I've done hardly any revision"
"Crapbuckets, I completely forgot Sharon's birthday"