Should Milagros walk the streets dressed like THAT? In one of the episodes of Muñeca Brava, our long-legged heroine gets all dolled up in a tight outfit to go dancing. Sister Cachetes isn't so sure about this. She says:
Pero igual me voy a quedar rezando para que no te pase nada, ¡y ojo!
But I'll nonetheless stay here praying that nothing happens to you, and careful!
Captions 15-16, Muñeca Brava 18 - La Apuesta - Part 4Play Caption
Ah, ¿sí? ¿Ojo con qué? ¿Ojo con qué? No me va a pasar nada.
Oh, yeah? Careful of what? Careful of what? Nothing is going to happen to me.
Captions 17-18, Muñeca Brava 18 - La Apuesta - Part 4Play Caption
In case you didn't realize that "ojo" literally means "eye," the good nun points to her eye as she speaks. In Argentina, this is a very common gesture that means, "careful!" or "watch out!".
In fact, you can silently point to your eye without saying a word and still be understood to be issuing a warning. Outside of Argentina, throughout Latin America and in Spain, the exclamation "¡Ojo!" is used and understood as well.
Note that Mili responds "¿Ojo con qué?" ("Careful of what?"). If you want to warn someone to be careful of something or someone in particular, use the preposition "con." Here are a few examples:
¡Ojo con los perros!
Careful of the dogs!
¡Ojo con los niños!
Watch out for the boys!
¡Ojo con los verbos irregulares en español!
Watch out for irregular verbs in Spanish!
Ojo could be replaced by guarda, and the meaning would be much the same.
¡Guarda con el escalón, te vas a tropezar!
Watch out for the step, you´re going to trip!
If you want to be more formal, you would go with cuidado. For example, you will often see this used on signs:
Cuidado con el perro
Beware of the dog