Definition of Energizer bunny in US English:

Energizer bunny

(also Energiser bunny)

noun

North American
  • A persistent or indefatigable person or phenomenon.

Origin

1990s; earliest use found in The Denver Post. From Energizer Bunny, the name of a battery-operated toy rabbit represented as never running out of energy, featured from 1989 in a television advertising campaign for batteries.

Pronunciation

Energizer bunny

/ˌɛnədʒʌɪzə ˈbʌni/