Here's what it likely means:
* To deal a severe blow or setback: It's probably used to describe something that causes significant pain, disappointment, or difficulty.
* To inflict humiliation or defeat: It might also be used to describe a situation where someone is made to feel embarrassed or unsuccessful.
Example:
"The team's loss in the playoffs really kicked it in the guts."
However, it's important to note:
* The idiom "kick it in the guts" is not commonly used.
* It's possible the speaker is using a slang term specific to their region or social group.
To be sure of its meaning, it's best to ask the speaker for clarification.