v.1. To block or close something, such as an opening or passage, with or as if with a wall: The safety inspector walled up the old mine shaft. The contractor walled the abandoned building up.
2. To confine or seal someone or something behind or as if behind a wall: The contractors walled up the wiring. In the fairy tale, a witch walled Rapunzel up in a tower.
3. To form a steep vertical surface. Used of an ocean wave: The wave walled up perfectly, and I dropped in.