Even though geeky hobbies are becoming more accepted in our general society, I sometimes still get gently teased by my relatives or coworkers for mentioning video games, RPGs or cosplay. What is the most polite and positive way to explain that these are totally normal adult hobbies?
It is easy to get defensive when people mock things you love. Telling them to STFU or mock something they love, like sports, "YOU WORSHIP TEENAGERS IN UNDER ARMOUR EVERY SATURDAY AND I'M THE WEIRD ONE?"
But that doesn't solve things in the long run, and certainly not in a professional setting.
A nice way to explain it would be to talk about creativity and escapism. Relate it to something they would do, reading a book, seeing a movie etc. But while those are typically solo endeavors, your interests allow you to be social and still escape.
I try and find a common ground starting point. You liked the Avengers movie? So do I....and more superhero stuff. I have found that men have an easier time accepting it because they have video game or superhero experience. Your average gossip girl sorority chick thinks I'm from another planet. Hence all the pub crawls I did in costume...
Ease in to talking about it - I'd probably start with authors or games or celebrities that more folks relate to. TV show and movie fandoms are more common than cosplay and conventions. There are 'muggle' folks who have become curious and more interested in cosplay after seeing the creativity and how much I enjoy it.
It also helps if there are super crazy/awkward coworkers or relatives to take the heat off you if you need to change the subject quick!
Working in an office environment, I used to dread answering the Monday morning question, "so what did you do this weekend?" I would be excited about some movie or gaming tournament or cosplay party I went to, but was always afraid to talk about it - except movies, that was usually safe. People at the office thought I was boring, because I kept such a big part of my life to myself. That's fine - with manager types, that's probably best.
Lately, though, I have had the courage to speak up more about my fandoms. People see my TARDIS iPhone case, or Rocket Raccoon desktop picture, and they ask me questions. It is a nice ice breaker. I've been fortunate that no one have given me crap about it lately, but if you keep your humor about you, you can just sling some (good natured) crap back about something they like and diffuse the situation.
As for family - I have enough dirt on all of them to stop that nonsense point blank if they give me a hard time! LOL.
I wouldn't tease other people's hobbies, even nicely-- just in case they get defensive (nerds aren't the only ones who are secretly insecure about their jam.) Lindsey is right about making it accessible; most people like action movies/superhero movies, or playing Mario Kart.
For the costuming, America has had a long history of costume parties. My super-barbie coworker is always asking me when DragonCon is, because she knows it's a big, giant costume party. All the 'Plastics' at my company loved the pictures of last years costumes.
For the especially sheltered, I explain it as "one of the world's biggest Halloween parties."
Hope this helps.
Good luck reader, and wave your geek flag proudly. After all, we rule the world.
Geek Girls, Inc.