memory burp
When your brain completely spaces out on something, usually in an embarrassing way, so you try to make light of the fact that you really screwed up or may in fact be heading toward dementia.
person a) Oops! Memory burp. Sorry I forgot to attend your wedding.
person b) Um yeah, bridesmaids aren't usually such forgetful twats.
person b) Um yeah, bridesmaids aren't usually such forgetful twats.