adj

• (chiefly British, Ireland, Australia, New Zealand, informal) Foolish, silly, stupid.
  "a daft idea"
• (chiefly British, Ireland, Australia, New Zealand, informal) Crazy, insane, mad.
  ""Ow, he is just a wood harum-scarum creature, that wad never take to his studies;—daft, sir, clean daft." / […] / "[W]owff—a wee bit by the East-Nook or sae; it's a common case—the ae half of the warld thinks t'other daft. I have met with folks in my day, that thought I was daft mysell;[…]" / "I cannot make out a word of his cursed brogue," said the Cumbrian justice; "can you, neighbour—eh? What can he mean by deft?" / "He means mad", said the party appealed to, thrown off his guard by impatience of this protracted discussion."
• (obsolete) Gentle, meek, mild.
  "There's mirth in the barn and the ha', the ha', / There's mirth in the barn and the ha': / There's quaffing and laughing, / And dancing and daffing; / And our young bride's daftest of a', of a', / And our young bride's daftest of a'."