off the record
• not made as an official or attributable statement.
• "all this is off the record"
Similar:
unofficial,
confidential,
in (strict) confidence,
not for publication,
not for public consumption,
not to be made public,
not for circulation,
not to be disclosed,
not to be mentioned,
private,
secret,
classified,
(to be kept) under wraps,
unofficially,
privately,
confidentially,
between ourselves,
sub rosa,
in petto,
entre nous,
between you,
me,
and the bedpost/gatepost,
under the rose,