What is the definition or description of: bad cholesterol?

LDL Cholesterol: Blood fats, cholesterol and triglyceride, are not soluble in water and are not transported in blood by themselves. Instead, lipids are carried by various lipoprotein particles. Low denisty lipoprotein (ldl) particles move into the artery wall and directly promote vascular disease. Cholesterol carried in LDL (ldl-c) is commonly used to estimate the number of "bad" LDL particles.

LDL Cholesterol: Low density lipoprotein cholesterol (ldl-c) is considered the "bad cholesterol". The purpose of ldl-c is to infer the number of cholesterol containing LDL particles (ldl-p) in the blood. Because cholesterol in LDL particles is highly variable LDL cholesterol (ldl-c) levels often underestimate ldl-p levels. When ldl-c and ldl-p disagree cvd risk tracks with ldl-p, not ldl-c.