1. Something that sticks out from its surroundings: Before they started renovating the walls in their living room, Maxine and Mark had to remove all the protrusions and leftover wallpaper in order to have a smooth surface to work on.
2. The act of thrusting forward or beyond the usual limit: Strong protrusions with his legs were necessary for the diver to get him back to the surface of the lake again.
3. Something that bulges out or projects from its surroundings: The protrusions on the side of the cliff made it possible for the mountain climber to get to the top by grabbing and holding on to each one as he climbed higher.