noun

• (Australia, New Zealand, slang, derogatory) A worthless person; a hooligan or lout.
  "'You flash hoon,' he went on, 'Kiddin' you're white, eh?[…].'"
• (Australia, slang, dated) A pimp.
  "When the girls were sick, the hoons would beat the shit out of them and put them back on the street."
• (Australia, New Zealand, slang) A person who drives excessively quickly, loudly or irresponsibly; a street drag racer often driving heavily customized cars.
  "Police have impounded an average of 10 cars a day since hoon laws were introduced by the State Government in June 2006. Hoon related offences include burnouts, doughnuts, drag racing, repeated driving while disqualified and high-level speeding. Offences are detailed in section 84C of the Road Safety Act 1986."
• (Australia, New Zealand, slang) An attempt or go at something.
  "The stars of Happytime Murders give Kiwi slang a hoon"

verb

• (especially Australia, New Zealand) To drive excessively quickly, loudly or irresponsibly.
  "[…] you've hooned off – it's fair to say hooned off – at quite a high speed."

noun

• (historical) A unit of weight (about 0.378125 of a gram, or 0.0133 of an ounce) used to measure opium in British-controlled parts of Asia; a candareen.
  "This abovementioned Chandoo or prepared opium for smoking is retailed by them [the East India Company] at 5 pice per hoon, equal to 8000 Spanish dollars per chest, and on the opposite or Queda shore the hoon is sold at 6 pice or 9,600 dollars, […]"

noun

• (India, historical) A pagoda, a type of gold coin.
  "The plaintiff in his plaint states, that the first and second defendants' elder brother, Soobbiya Shetty, on the 8th Ashweeja Bahoola of the year Veya, mortgaged to him, for 2½ hoons, his two slaves, viz. a female Dher, named Honnoo, and a male Pardeshey, together with their offspring, and made them over to him; that while they were in his possession, Soobba Shetty died, and the first and the second defendants succeeding to his (Soobba Shetty's) property, they further executed a document to him for hoons 4-8-12, on account of a balance against themselves of rice, &c., making a total mortgage on the slaves of hoons 7-3-12."