| Noun | 1. | pachyderma - thickening of the skin (usually unilateral on an extremity) caused by congenital enlargement of lymph vessel and lymph vessel obstruction congenital disease, genetic abnormality, genetic defect, genetic disease, genetic disorder, hereditary condition, hereditary disease, inherited disease, inherited disorder - a disease or disorder that is inherited genetically elephantiasis - hypertrophy of certain body parts (usually legs and scrotum); the end state of the disease filariasis |