noun, na-adjective, noun which may take the genitive case particle 'no'
immediately effective; having an instant effect
Describes something that works right away, often used for remedies, measures, or advice that produce noticeable results without delay.
この薬は風邪に効果覿面だ。
This medicine works immediately for colds.
彼のアドバイスは効果覿面だった。
His advice had an instant effect.
A yojijukugo composed of 効果 (effect) and 覿面 (immediate, directly visible). 覿面 is a rare compound meaning 'immediately apparent' or 'instant'. The exact historical derivation is uncertain, but the phrase is conventionally used to mean 'immediate effect'.