Here are some possibilities and what they could mean:
* "Mierda de cuál": This would mean "What kind of crap" or "Which crap", expressing strong disapproval or disgust. This phrase is very informal and often used in a humorous or sarcastic way.
* "Mierda de cual...": This could be the start of a sentence where "cual" is a pronoun referring to something previously mentioned. For example: "Mierda de cual... me estás hablando?" ("What kind of crap... are you talking about?")
* "Mierda de cuál...": This could be an incomplete sentence where "cual" is a pronoun referring to something that needs to be specified. For example: "Mierda de cuál... esa película es terrible." ("What kind of crap... that movie is terrible.")
If you provide more context, I can help you understand what the phrase means!