in terrorem

adverb or adjective | \ ˌin-te-ˈrōr-əm, -em \ | in ter·ror·em
  1. : by way of threat or intimidation : serving or intended to threaten or intimidate overbroad covenants not to compete which have in terrorem effect on employees —J. D. Calamari and J. M. Perillo

    Note: In terrorem is most commonly used to describe a condition in a will that threatens an heir with forfeiture if he or she challenges the validity of the will.