noun

• (slang, UK) The penis when enclosed in clothing.
  "The campaign tagline, 'I've got a tiny packet', is written across [Linford] Christie's trademark impressively muscled upper body. 'Tiny packet' makes us remember that Linford is known for his 'lunchbox' from his heyday as a sprinter because of the bulge apparent in his lycra shorts. His lunchbox and now his tiny packet allude to the diminishing of black men to just their genitals[…]"
• (especially Asia) A lunch packaged in a disposable box to be taken away to eat.
  "Jack was carrying his lunchbox with him."
• (computing, slang) A luggable; an early laptop computer, usually a unit with a handle and a fold-out keyboard.
  "You'll find a mix among clamshell laptops for strong laps, lunchboxes, and sewing-machine configurations; the latter two designs typically have detachable keyboards."
• (slang) A simple portable transmitter sometimes used in phreaking.