Used when something has been built up with huge anticipation and then fails miserably.
Used in similar context to 'tits-up'. Based on the first day failings of UK's Heathrow Terminal 5 in which the 15minute check in and security pass ended up at 19hours long!
'Dude, sex with Anna. I thought she'd be good but it was totally T5'
'The Patriots went T-5 against the Giants today'
'So the Iraq war has gone T-5'
'The only thing more T-5 than this is Hiliary Clintons Campaign'