1.
to let something slip; to blurt out; to make a slip of the tongue
To accidentally say something that should have been kept secret or that one did not intend to reveal. Literally 'to let one's mouth slide.'
つい口を滑らせてしまった。
I accidentally let it slip.
秘密を知っていたが、口を滑らせてしまった。
I knew the secret but ended up blurting it out.
サプライズパーティーのことを口を滑らせて本人に言ってしまった。
I accidentally let it slip to the person about the surprise party.
USAGE:
This expression is almost always used with てしまう to convey the accidental, regrettable nature of the slip. The subject is always the person who blurted something out.
GRAMMAR:
The verb 滑らす is a godan verb. In practice, the te-form 口を滑らせて is the most common form encountered.
SIMILAR EXPRESSIONS:
- うっかり言ってしまう (to carelessly say something)
- 失言する (to make a verbal gaffe — more formal)