Русско-англо-русский юридический словарь

If the obligations of both parties arise from the same contract, the first party may also set off its obligation against an obligation of the other party which is not ascertained as to its existence or to its amount. ( Article 8.1 (Conditions of set-off) - UNIDROIT)

A juridical fact is a fact that is recognized by law as an event that has legal meaning and that will therefore set off a particular legal reaction. (Legal System of Civil Law in the Netherlands)

Set off in its simplest form is generally understood by legal practitioners and laypersons alike - it refers to the reduction or extinguishment of a claim by a co-existing counter-claim. Thus, if Justinian owes £100 to Gaius and Gaius owes £80 to Justinian, set off can intervene to reduce the co-existing claims to a single claim for £20 owed by Justinian to Gaius. (Morton Fraser Lawyers)

For such a key figure in crime fiction, the snitch, or stool pigeon, is rarely given much prominence. He is forever shoved to the sidelines, his motives tied up in a simple bundle of malevolence, condemned to look on as his shabby interventions set off or disrupt plots bigger than his own. (The Independent)