tip off

tip off  {v.},  {informal}

Говорить то, что не является общеизвестным; сообщать секретные факты; предупреждать.

The class president tipped off the class that it was the superintendent's birthday.

The thieves did not rob the bank as planned because someone tipped them off that it was being watched by the police.

Ср.: PUT WISE.