i Register
In some senses, yahoo is marked as derogatory, informal. Watch for register when choosing this word.
noun
A rough, coarse, loud or uncouth individual.
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.
intj
An exclamation of joy or enjoyment.
"Yahoooooo! Give her some stick!"
A battle cry.
verb
To give a cry of yahoo.