IPA: /ˈʃɜːrfaɪər/
KK: /ˈʃʊrˌfaɪər/
Certain to succeed or achieve the desired outcome.
This plan is a surefire way to win the competition.
A method or plan that is guaranteed to succeed or achieve a desired result.
The new marketing strategy is a surefire way to increase sales.
Surefire → It is formed from "sure" (from Old English *sūre*, meaning certain or secure) and "fire" (from Old English *fyr*, meaning fire). The word "surefire" means certain to succeed or guaranteed to work, as if it is as reliable as fire.
Think of something that is 'certain' ('sure') to succeed, just like how fire is a reliable source of heat and light.