To wallow is to roll about in something, as a pig wallows in mud or a billionaire wallows in money.
Wallow can be used to describe a physical action or an emotional state. If you cry "Woe is me!" one too many times, you might be accused of wallowing in self-pity. Because of its association with the much-maligned pig, wallow often has a negative, insulting tone. So, rather than wallowing in that pile of money once you've won the lottery, try bathing or wading in it instead.