1. (noun) a leading instance in its field

• pacesetter

2. (noun) a specialized bit of heart tissue that controls the heartbeat

• cardiac pacemaker
• sa node
• sinoatrial node

3. (noun) an implanted electronic device that takes over the function of the natural cardiac pacemaker

• artificial pacemaker

4. (noun) a horse used to set the pace in racing

• pacer
• pacesetter

1. (noun) a leading instance in its field

• example
• exemplar
• good example
• model

2. (noun) a specialized bit of heart tissue that controls the heartbeat

• cardiac muscle
• heart muscle

3. (noun) an implanted electronic device that takes over the function of the natural cardiac pacemaker

• electronic device

4. (noun) a horse used to set the pace in racing

• bangtail
• race horse
• racehorse

1. (noun) a horse used to set the pace in racing

• pace