Cooked Rice, Food
The kanji and the word are exactly the same. That means they share meanings as well. It also refers to cooked rice, because you gotta eat cooked rice with every meal, so it's basically synonymous with "meal" itself.
This word has a slightly gruff feel to it so it's used mostly in informal situations.
Since this word is made up of a single kanji, it should use the kun'yomi reading. When learning the kanji, you didn't learn that reading, so here's a mnemonic to help you with this word: You're eating a meal... MMmm, delicious! What are you eating? Well, it's a Mesh (めし) net. Taste the mesh net. It tastes terrible. This is a bad meal. Feel it in your mouth. It's weird and meshy.
Oh no. I forgot to cook rice.
Koichi would rather work for Tofugu than eat.
Those were some really stinky-smelling meals! I never want to go back to prison.