I'm assuming you meant "peached" as a verb, so here are two possible definitions:
To inform on someone, usually to the authorities, by revealing something they have done wrong or illegal. Example: "He peached on his colleagues to get a lighter sentence for himself."
To cook a fruit (usually a peach) in boiling water for a short time to make it easier to peel or to soften it before using it in a recipe. Example: "First, you need to peel and peach and then peach it for a few minutes before making the pie filling."