Lat In Saxon law. A threefold necessity or burden. A term used to denote the three things from contributing to the performance of which no lands were exempted, viz., pontis rcpara- tio, (the repair of bridges,) areis constructio, (the building of castles,) et expeditio contra hostcm, (military service agaiust an enemy.) 1 Bl. Comm. 203, 357.