to reveal something secret unintentionally
うっかり秘密を漏らす (ukkari himitsu o morasu)
"Don’t let on that you know about the plan."
"計画について知っていることを言わないでください。" (keikaku ni tsuite shitte iru koto o iwanai de kudasai)
to reintroduce something gradually
to make something more interesting or lively
Refusing to answer a question
to secure something so it cannot change
feeling hopeless and defeated
to be very familiar with something; to have a thorough under...
