The word mierda means ‘shit’. It applies specifically to human feces, but can also be used for the poop of some animals. And it refers, like ‘shit’ in English does, to a variety of dirty, disgusting, or worthless things, as well as serving as an interjection to express indignation or frustration.
The word ‘mierda’ is of course vulgar and offensive, roughly to the same degree that ‘shit’ is in English. But it is used differently. Because of its many uses, let’s start with what the Real Academia Española gives for this word.
1. f. Excremento humano.
2. f. Excremento de algunos animales.
3. f. coloq. Grasa, suciedad o porquería que se pega a la ropa o a otra cosa.
4. f. coloq. Cosa sin valor o mal hecha.
5. com. coloq. Persona sin cualidades ni méritos.
1. interj. vulg. Expresa contrariedad o indignación.
The more common uses of ‘mierda’ are very similar to how ‘shit’ is used in English, as seen below.
• Hay mucha mierda debajo de la alfombra. (There is a lot of shit/crap under the carpet.)
• Tiene una oficina llena de mierda. (His (or her) office is filthy/disgusting.)
• Es una mierda de carro. (The car is a piece of shit.)
• Un libro de mierda. (A shitty book)
Also similar to ‘shit’ in English is the use of ‘mierda’ as an interjection to express surprise, anger, or frustration.
• ¡Mierda! Ya me he olvidado. (Shit! I forgot!)
• ¡Una mierda! (Get lost! Piss off! [said when someone asks you to do something])
There are several common idioms that use ‘mierda’ as well, though which you will hear depends on what part of the Spanish-speaking world you are in.
• ¡Vete a la mierda! (Go to hell! Piss off!)
• Le mandé a la mierda! (I told him to shove off!)
Like ‘shit’ in English, ‘mierda’ is also used to refer to hashish or other drugs, though this too varies depending on where you are.
As with all curses, be very careful when using any form of mierda. Even native speakers can cause offense, so non-natives are usually better off just avoiding them. But ‘mierda’ and its accompanying idioms are so common that you have to know them.