As you learned in Spanish class, the word oso means bear, the animal. However, oso is commonly used to talk informally about embarrassing, cringe-worthy situations and experiences. The most common usage is ¡Qué oso!
The exclamation ¡Qué oso! basically means ¡Qué pena! How embarrassing! It works for something idiotic that you yourself did — or for someone else’s embarrassing incident, in which case ¡Qué oso! becomes a synonym for ¡Qué pena ajena!
Public Service Announcement, Mexico City subway
Hacer el oso
Hacer el oso means create an embarrassing situation, for example, by falling down at a party and spilling your drink everywhere. No quiero llegar antes de tiempo para no hacer el oso. I don’t want to look stupid by arriving early. Note that you aren’t making yourself into a bear by doing something stupid. Oso seems to refer to the misstep, the faux pax, itself. That’s why we say hacer el oso without the pronoun te.
El peor oso
Here’s an example of oso with the verb pasar: Me hiciste pasar por el peor oso de mi vida, amiga. You just made me go through the most embarrassing experience of my life.
Me da oso
As with pena, oso can be used with the verb dar: Es que me da oso. I’d be embarrassed to do that. That’s why I won’t do that. Here, oso is about the emotion of embarrassment rather than the situation itself.
When to use oso
Not everyone uses slang of this type. For some reason I associate oso with the speech of teenage girls and fresas. To avoid making a fool of yourself, wait and see if the people you hang out with use oso like this. If they do, go for it. Otherwise, stick to ¡Qué pena! In any event, it is useful to know what oso means when you hear it in the wild.
Oso de pelucheWhile were on the subject of osos, I’ll mention that teddy bear is oso de peluche or osito de peluche, since stuffed animals (AmE) / soft toys (BrE) are called peluches in general.
Within gay circles, a man who is large and hairy may be referred to as an oso, paralleling the English term, bear.