1. causing detriment; damaging; harmful.
1. a detrimental person or thing.
It is detrimental to your health to smoke a pack of cigarettes a day!
I must relate to you the reason why I chose this word! I was working crew for the One Act plays at my college this weekend. At the end of the first performance, the stage manager summoned me and tried to tell me that I needed to make sure everything went back to its proper place. This, however, is how she said it: "It is detrimental that you return all the set pieces back to their places, because when you don't, everyone trips over them." So according to her, it's very very bad to put things back in their right places. I believe she was looking for the word 'imperative' or something like it. I was so very distracted by the fact that she completely misused the word (and because I was trying so hard not to laugh) while she was trying to scold me that I couldn't hear anything else she said.
So, kids, the moral of this story is to not use the word 'detrimental' as this unfortunate stage manager did.
General Edit: Oh my! It has suddenly been revealed that there seems to be a widespread feeling of discontent about the recent choice of words! I suppose this calls for a widespread attempt to remedy the feeling.