Dr. Armaan,
Did you mean a new word or a new symantics (i.e. meaning/idea/concept) ? Have you checked that some other synonym of the word already exists under an existing symantics and your new word can be added there? If you want to add a new word, you must search the all the possible synonyms of the word. Once you find the symantics under a synonym, you can follow the instructions given there.
Once you are confirmed that the symantics does not exist and your new word can not be added anywhere, then only you go ahead and create a new symantics. However, if you want to add a new symantics, you can do that only if you are a Level=2 contributor.... we had to put in this restriction to avoid creation of duplicated symantics.
Hope you understand.
Thanks,
Bikram