Culo is the slang way to say butt, but it also can be use to say someone is very mean or uncooperative. You can also use another form of culo for this last meaning, wich its “Culero”, but you can also use this last one to say something isnt good, or that you dislike it.
Cuando era niño y hacia bromas a mi hermano, mi madre me pegaba nalgadas en el culo/ When i was a child, and I made pranks to my brother, my mom used to spankme in the butt.
No comas en ese restaurant, la comida esta culera/ Don’t eat on that restaurant. The food is bad
Ese wey golpea perros, es bien culo-culero/That dude hits dogs, he is very mean.
I hope you have learned something new, about the spanish that real Mexicans talk on their everyday life.
If you want to improve your Spanish, I also give tutoring lessons on skype using this page that host many teachers from all over the world, and while I don’t really do grammar, I can help with conversation and doubts about the language. Also, if you are interested in any language besides spanish, there are teachers and tutors for any language there.