Hawt = A late 1940's and early 1950's acronym for "Having A Wonderful Time."
Now the word is used on the internet as slang for something reeeeally hot.
Actress Sienna Miller looked HAWT last week at the opening night of the new Broadway play ‘Orphans’ (starring her beau Tom Sturridge). The yummy mummy wore a classic belted Burberry trench coat whilst wearing her heart on her sleeve with the Burberry Prorsum Heart Print Calfskin Drawcord Bag as she posed for photographers in NYC. The outfit subsequently caused speculation that the gorgeous couple have been hired as the British brand’s A/W’13 faces… I would heart that.