Yabber – to talk too much (if you were accused of yabbering on, you would be talking too much)
Yabbie – a small freshwater crayfish
Yakka –a term for work and usually used to describe hard work (being hard yakka)
Yank – an American person
Yank tank – a large American  car (think large SUV)
Yobbo – an uncouth Aussie, usually dressed in shorts, flip-flops and a singlet. The person invariably drinks too much, belches and f**ts no matter who is present and has little regard for manners. An Aussie calling another Aussie a Yobbo is akin to American calling another American a Redneck.
You beaut or beauty – something that is very good
Youse – is you (plural). For example, instead of asking “…have you guys got any spare bread” you would say “…have youse got any spare bread”? The use of the word is definitely confined to those poorly educated or who are “ockers”.
Yowie – the Aussie version of a large mythical creature


Zebra crossing – a pedestrian crossing on a roadway
Zeds, to grab – to sleep (zeds Down Under are zees in the US)
Zilch – means nothing
Zillions – a large number where “millions” is insufficient to describe it
Zonked – totally exhausted