from
Bouvier's Law Dictionary, Revised 6th Ed (1856)
IN TERROREM. By way of threat, terror, or warning. For example, when a
legacy is given to a person upon condition not to dispute the validity or the
dispositions in wills and testaments, the conditions are not in general
obligatory, but only in terrorem; if, therefore, there exist probabilis
causa litigandi, the non-observance of the conditions will not be a
forfeiture. 2 Vern. 90; 1 Hill. Ab. 253; 3 P. Wms. 344; 1 Atk. 404. But when
the acquiescence of the legatee appears to be a material ingredient in the
gift, the bequest is only quousque the legatee shall refrain from disturbing
the will. 2 P. Wms. 52; 2 Ventr. 352. For cases of legacies given to a wife
while she shall continue unmarried, see 1 Madd. R. 590; 1 Rop. Leg. 558.