noun

• (derogatory) A rough, coarse, loud or uncouth individual.
• (cryptozoology) A humanoid cryptid said to exist in parts of eastern Australia, and also reported in the Bahamas.
  "1835, James Holman, Travels, quoted by Malcolm Smith, Bunyips and Bigfoots (Millennium Books, 1996, →ISBN), who notes that the Australian sense almost certainly derives from Gulliver's Travels, despite Holman's report The natives are greatly terrrified by the sight of a person in a mask calling him "devil" or Yah-hoo, which signifies evil spirit."

verb

• (transitive, intransitive, informal) To give a cry of yahoo.

noun

• (fiction) One of a race of brutes, who look and act similar to men, inhabiting the same land as the civilized Houyhnhnms.
  "I therefore often begged his Favour to let me go among the Herds of Yahoos in the Neighbourhood, to which he always very graciouſly conſented, being perfectly convinced, that the Hatred I bore thoſe Brutes, would never ſuffer me to be corrupted by them; […]"

noun

• (informal) An employee of the Internet company Yahoo!.
  "But having two beaming Chief Yahoos on the cover is an implied seal of approval."