1. Medical engineering. An insulated conductor connected to an electrical device. It is used in recording changes in electric potential, created by the activity of an organ, such as the heart (electrocardiography (ECG), cardiac pacemaker) or the brain (electroencephalography).

2. Chemistry. Chemical element with the symbol Pb. A soft, bluish-white, dense metallic element. Excessive ingestion or absorption causes lead poisoning.

meaning of to lead: to conduct, to bring, or to induce