We say "we own a timeshare at Disneyworld." It explains the concept best for what I want to get across to people (which is "why do you go to Disney so often" and "How much do you like Disney." - "we own a timeshare at WDW" answers both those questions.
Most people don't care about the ins and outs of points vs set weeks, housekeeping, dues, benefits, home resorts, etc. about as much as you care about what flowers are in your cousin's wedding bouquet - which is to say "don't give people more information than they asked for - they think its boring."
If I say "we own a timeshare at Disney" and they then ask questions about it, I will follow up with an explaination of the program. That has never happened in five years of ownership.
And if the word "timeshare" carries negative connotations and they want to think less of me, that's their problem.