I marked a student down for using the word chillax as I believed it to not be a word. Later on they approach me on the issue and show me that it is indeed in the dictionary.
Every fiber of my being screams that it shouldn't be used. Even this site underlines the word saying it's not correct.
According to all dictionary entries I've seen it's not even listed as slang, only informal.
What is a valid reason that chillax shouldn't be used?
Perhaps because it's informal but that doesn't seem like a valid reason as there are plenty of informal words that are quite common and I wouldn't think to mark them down for words such as phone or kids.