Definition of all-timer in English:

all-timer

noun

US
  • 1Sport
    Sport (originally and chiefly Baseball). A sportsperson who has achieved an unsurpassed or unequalled record during their career or who is otherwise considered memorable for some accomplishment.

  • 2An outstanding or classic example of its kind; something considered to have enduring value, significance, or popularity.

Origin

Late 19th century (in an earlier sense). From all-time + -er.

Pronunciation

all-timer

/ˌɔːlˈtʌɪmə/