This is the 6771st most frequent Spanish word.
coso
A vague term for "thing" or "stuff."
In this use, 'coso' expresses a general, informal reference to an object or a particular item.
¡Qué coso tan extraño encontrarás en ese lugar!
What a strange thing you will find in that place!
Here, 'coso' is used informally to refer to an object whose name is unknown or irrelevant.
Este coso no funciona como se esperaba.
This thing does not work as expected.
In this sentence, 'coso' is used colloquially to refer to an unspecified item.