Ectomorph
An individual having a lean, slightly muscular body build in which tissues derived from the embryonic ectoderm predominate
Endomorph
An individual characterized by relative prominence of the abdomen and other soft body parts developed from the embryonic endodermal layer.
Mesomorph
An individual with a robust, muscular body build caused by the predominance of structures developed from the embryonic mesodermal layer.
Definations are from American Heritage Dictonary hope this helps.