From Longman Dictionary of Contemporary Englishslip something ↔ in phrasal verbto use a word or say something without attracting too much attention He had slipped in a few jokes to liven the speech up. → slip→ See Verb table
Examples from the Corpus
slip in• When the Cats slipped to fifth in a tough Pac-10 race, the doomsayers fired up their engines.• Did the ISAs slip up in Althusser's case?• Stars dusted the sky but it was an attacker's moon which slipped treacherously in and out of the clouds.• Chris Tavaré at first slip gets in on a piece of history.• And, like her father, it slipped away in one explosive moment.• Cambridge have slipped back in recent weeks.• The Clinton administration has beefed up the Border Patrol, but illegals still are slipping though in unacceptable numbers.• Just slip it in your bag or briefcase. 