Definition of old thing in English:

old thing

noun

informal
  • A familiar form of address.

    ‘sorry if I woke you, old thing’
    • ‘Oh come on now, old thing, never say die, every little counts, etc.’
    • ‘‘Don't worry, old thing,’ she told the nervously pacing and swaybacked animal.’
    • ‘You're obviously lying to us, old thing, or you've taken a berth on the HMS Bedlam.’