Originally used almost exclusively in England as a toast accompanied by a clink of glasses or raising of same, has come to mean almost anything an English person (particularly hooray Henriettas) wants it to mean rather in the style of shit or cool, but usually with ironic overtones.
A prevalent term in some social groups withing Australia, and occasionally Britain. In simple terms, this phrase is said whenever something negative occurs.
Gambler - Just lost $50 because the Suns won. Not cheers!
Student - Had to go to school today regardless of my flu. Not cheers at all. Commuter - Couldn't get myself a seat on the train this morning. Not cheers.
A word used by Britons on any occasion, covering any meaning from 'thanks', 'hello', 'no problem', to 'an alien just raped your chinchilla in the left corner of my blue garden shed'. Usually followed by the term 'mate', which is also 100% devoid of semantic content and meaning. This phenomenon is taken by some continental scholars as strong evidence that all Britons are telepathic.