something that sticks out from a surface

If the plant has been infected you will see dark protuberances along the stems. 如果这种植物感染了病菌，你会看到它的茎上出现黑色的凸出物。

a projection or swelling on a part of the body such as the chin or the eyebrow

Bunions are bony protuberances that stick out on either side of the foot. 拇趾囊肿是脚侧的骨样突出物。