Definition from Wiktionary, the free dictionary
troppo (not comparable)
- (Australia, slang, with "go") Crazy, mad, strangely behaving; especially as attributed to hot weather.
- Barry′s gone troppo and married that sheila he′s only known for two weeks.
- After three months by himself on his ‘dream’ tropical island he went troppo and smashed all the equipment.
- 1989, Rosie Boycott, All for Love, page 163,
- ‘ […] She calls these rehearsals my singing lessons - but at least I don′t have people rushing in thinking I′ve gone troppo . . .’
- ‘Except me.’ Violet′s smile lingered as she gazed at him.
- 2009, Paul Tapp, Disquiet - the Justifiable Homicide of an Australian Vietnam Veteran, page 121,
- For a lone Digger gone troppo, as Joe is deemed to have done, it is a realistic scenario.
Usage notes 
Used in the verb go troppo — to go crazy, to act strangely, as due to tropical heat.
- ^ 1978, G.A.Wilkes, A Dictionary of Australian Colloquialisms, Fontana.
- ^ Australian National Dictionary Centre Home » Australian words » Meanings and origins of Australian words and idioms » T
From the Italian, and also from French trop.