noun
verbal intervention
In finance, refers to central bank or government officials using statements to influence markets without actual market operations.
日銀総裁の口先介入で円高が一時的に止まった。
The yen's rise temporarily halted due to verbal intervention by the BOJ governor.
為替介入 is actual market intervention (buying/selling currency), while 口先介入 is only verbal.
Compound of 口先 (lip service, words) and 介入 (intervention). The exact origin is uncertain, but it is a modern financial term.