Let's review some unique Spanish words that you may not have heard of before. 

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Spanish uses a specific word to describe the rheum (more commonly known as "sleep" in English) found in the corner of the eye after sleeping: lagaña (also legaña). This odd word has an uncertain origin, though some experts believe it to be inherited from a Paleohispanic language! It's important to note that lagaña is not a specialized term as "rheum" is in English, but a common word used in everyday conversations:

Esto es que una... una de las glándulas que se encarga de fabricar la lagaña...

This is because one... one of the glands that is in charge of producing rheum...

Caption 79, Animales en familia - La operación de Yaki

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Other unique Spanish words related to the body are entrecejo (the space between the eyebrows).
 

Y esta parte se llama entrecejo.

And this part is called "entrecejo" [the space between the eyebrows].

Caption 16, Marta de Madrid - El cuerpo - La cabeza

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and chapas (blush, the pink tinge on the cheeks):
 

...para obtener las clásicas chapitas de Pikachu.

...to get the classic Pikachu rosy cheeks.

Caption 25, Manos a la obra - Separadores de libros: Pikachu

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Do you know any Spanish words or expressions used to describe different types of rain? The expressions está chispeando and está lloviznando both mean "it's drizzling." The verb chispear comes from the noun chispa (spark), while the verb lloviznar comes from the noun llovizna (drizzle). On the other end, when the rain is really heavy, people may use the noun tormenta (storm) to describe it, though aguacero (downpour) is also very common:
 

Aguacero de mayo, me lleva, papá

May downpour, it's taking me away, man

Caption 44, Kikirikí - Animales

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Of course, people also use idiomatic expressions to talk about the rain. One example is llueve a cántaros (the equivalent of "it's raining cats and dogs," literally "it's raining as if pitchers were being poured from the sky"). Other words that you may want to explore on your own are: chubasco (a very intense, windy storm) and chaparrón (an intense, sudden, and short storm).
 
Another interesting set of unique Spanish words is the group used to talk about family in-laws, a list that is quite big, as you can imagine. It's not only suegro, suegra (father- and mother-in-law), but also yerno, nuera (son- and daughter-in-law), cuñado, cuñada (brother- or sister-in-law), and even concuño, concuña (brother, husband, sister, or wife of one's brother-in-law or sister-in-law)!

Es una champiñonera tradicional que estableció mi suegro.

It's a traditional mushroom farm that my father-in-law established.

Caption 6, La Champiñonera - El cultivo de champiñón

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Estaba en la casa de mi suegra y mi cuñada,

I was in my mother-in-law's house, and my sister-in-law,

la hermana de mi marido...

my husband's sister...

Caption 52, Biografía - Natalia Oreiro

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Interesting tidbit: The equivalent of "in-law family" in Spanish is familia política. You can use the adjective político (political) to describe less close relatives such as primo político (in-law cousin).