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.
Common way for a Kiwi to (1) say thanks, (2) sign off an email/memo/will ("cheers,") or (3) what we shout when clanging our handles of booze together in a moment of comaderie.
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.
"I've just told your bird you're bonking her sister."
"Oh cheers, mate."