1. A spheric particle of lipid substance suspended in an aqueous medium within a tissue.
2. Any small, roughly spheric artificial vesicle consisting of a lipid bilayer enclosing some of the suspending medium.
The definition information for liposome is provided by Stedman's. You can search our medical dictionary here.
Stedman's, part of Lippincott Williams & Wilkins, provides a comprehensive line of health-science publications for healthcare professionals and medical students.