To an extent, I agree. However, most writers will play off the meaning already established for a word, choosing that word because of its prior meaning and then redirecting the meaning rather than establishing a whole new meaning.
Of the words owlcroft listed,
sorceror
wizard
mage
magus-- Powerful magic users. The last two would seem to be the strongest of magic users, and the words have the connotation for me of scholar as well as magic user (I admit, I'd like to hit the OED to see what that has to say about these, but I'll blunder on first.)
warlock
witch -- magic users who may be aligned with dark forces; these are words, especially the latter, which Christian mythology colors
magician
conjuror -- might be magic users, might be circus performers; there's the taint of show biz to these words
enchanter -- user of magic that alters the perceptions of others, plays with the mind.
Randy M.
I think this is a fair assessment but, I'll chime in with my 2 cents.
sorceror Extremely powerful and scholar in magic
wizard Similar to sorceror but older perhaps an honorary title for someone who is up there in years. (IE: Fizbin and Gandalf)
mage Learned and in their middle years
magus Another title for someone strong/gifted in the magical arts.
I also think that of the terms above they can be used interchangably.
warlock The term for a male witch
witch a woman with no formal training but engages in the magical arts through personal discovery or latent/innate ability. Unlike the western thought where these two are usually seen as people with evil intent. I prefer to see them as having the ability of going either way depending upon their personal goals.
magician person who has an affinity towards magic and has some ability but overall more of a dabbler in the arts.
conjuror Slightly darker than a warlock in that they have very little if any training but have the ability to call upon minions to do their bidding.
enchanter for some reason I see this as a female only talent. The ability to sway or alter a persons thoughts through nefarious means ie: chemical, sexual, etc. It seems that when you come in close proximity to the enchanter you loose the ability to hold your own opinion and are powerless if you are not strong willed/minded.
I really think that it depends on how an author uses the terms within their novel that define the terms. Of course we all have our own mental picture of what the characters look like and their power levels. So to a certain extent it is define by what we read and what we see in our minds that truly define the term.
It is an interesting topic that is for sure and I would love to hear other people's opinion on the subject.