Delación has at least two “legal” meanings, one used in criminal law contexts that would likely be familiar to non-lawyers, and one whose meaning is clearly limited to inheritance law (Derecho de sucesiones). As a criminal law term delación is a synonym of acusación or denuncia, being defined in the Diccionario del español jurídico (DEJ) as revelación de datos que permiten identificar al culpable.
But in inheritance law its meaning is quite different, delación referring to the offer of an inheritance to prospective heirs so that they may accept or reject it. Quoting a Spanish Supreme Court opinion, the DEJ explains that delación is an ofrecimiento de la herencia al heredero, que da lugar a un derecho subjetivo, ius delationis, que faculta la adquisición por la aceptación. In that regard ius delationis denotes an heir’s right to accept or reject an inheritance and, in the meantime, to take measures to preserve the deceased’s estate.