breach of trust. Breach of trust means a breach of any duty imposed on a trustee, as such, by any law for the time being in force. An improper act. neglect or default on the part of a trustee n regard to his trust, either in disregard to the terms of the trust, or the rules of equity. The measure of the trustees liability is the loss caused thereby to the trust estate. Any profit accruing from a breach of trust, e.g. improper speculation or trading with the trust assets, belongs to the trust estate.