This is the 4228th most frequent Spanish word.
meloni
The word "meloni" does not exist in standard Spanish.
Here, 'melón' refers to the fruit 'melon'.
Me encanta comer un melón fresco en verano.
I love eating fresh melon in summer.
In this context, 'melón' is used figuratively to describe someone as being slow or dull in understanding.
Juan es un melón para entender matemáticas.
Juan is a melon at understanding mathematics.
Once again, 'melón' is used in its primary sense to mean the fruit 'melon'.