1. An abnormal or unwanted growth or outgrowth on the body or a plant; a protuberance.
Usage: Usually plural; can be medical or botanical
2. Something regarded as an undesirable or superfluous addition; an ugly or offensive feature.
Usage: Figurative use; often used to describe something unwanted in a structure, system, or society

Examples

• The dermatologist removed the skin excrescences from the patient's arm.
• Warts and other excrescences can be treated with various medical procedures.
• The architect criticized the modern additions as ugly excrescences on the historic building.
• The critic viewed the subplot as an excrescence that detracted from the main narrative.
• Barnacles and other marine excrescences covered the ship's hull.
• The old city had accumulated many architectural excrescences over the centuries.