A document created by a person while still in relatively good mental condition stating in advance his or her wishes for medical treatment if and when he or she is no longer able to communicate and provide informed consent; see also advance directive, durable power of attorney. L.L.C. ABBRV.Limited liability company. LL.M.ABBRV.(Latin)Legum Magister. Lloyd's of London.N. A group of private insurance underwriters based in London, England, that originally specialized in marine insurance but now ...