Trust definition: obligation annexed to ownership imposing trustee duties to hold property for beneficiaries' benefit. A trust is an obligation annexed to ownership whereby an owner who reposes or declares confidence accepts that another (the trustee) will hold trust-property for the benefit of a beneficiary; the beneficiary's right against the trustee is the beneficial interest, and the instrument by which the trust is declared is the instrument of trust; failure of a trustee to perform duties imposed by law is a breach of trust, while registration and notice are defined by prevailing registration law and standards of actual or constructive knowledge.