MFI
noun
1
MI5, the UK's security intelligence agency. From the name of the retail chain that pioneered self-assembly furniture in the UK, and became the butt of many jokes UK, 2002.
2
a very large myocardial infarction; a major heart attack. Medical slang, elaborating the conventional abbreviation for the condition, MI, with F for, presumably, -FUCKING-. MFI is also a well-known flat-pack furniture retailer UK, 2002