I am using the tag “archaic” to two purposes.  First, if the OED calls a word “archaic”, then “archaic” it is tagged!  Second, I am using it as an umbrella term to embrace the obsolete words and the rare words as well (as they are labeled by OED).  One tag to mean “old”.  If you see “rare” or “obsolete”, know that that’s the dictionary’s primary classification of the word in question (not that there aren’t a few words which have earned many different OED labels!).