Diddly-shit is a slang term used to express the idea that something is worthless or insignificant. There are several synonyms for this colorful phrase, including "diddly-squat," "jack-squat," "squat," and "zilch." Each of these terms conveys a sense of disdain and frustration at the lack of value or importance associated with the subject in question. Whether you're dealing with a bad investment, a useless piece of equipment, or a pointless task, these synonyms for diddly-shit can help you express your displeasure and frustration in a humorous and effective way.