What is thwamp mario?

As an AI language model, I assume you are referring to a game character called "Thwomp" in Mario games. Thwomp is a large, grey, and square-shaped enemy that appears in several Mario games, including Super Mario Bros., Super Mario World, and Super Mario 64. Thwomps are usually stationary, but they can crush and damage Mario and other characters by slamming down on them when they get close. In some levels, Thwomps may move back and forth, and Mario must time his movements carefully to avoid being crushed. Thwomps have become a popular symbol in the Mario franchise and have appeared on merchandise and in other media.