Has anyone heard of this? Just got an invite to my cousin's twin boy's B'nai Mitzvah and this was added on the reception card. Service is in the morning and the party is 7pm - 11pm - what would one wear to this? I'm kind of just sitting here shaking my head...I'm heard of some of the more "creative" (fake?) attire styles (smart casual, sport casual, creative black tie) but never had heard of cowboy casual.
Should I wear cowboy boots, a jean skirt, and have a length of rope coiled at my hip?

Re: "Cowboy Casual"?
Edited to add: The above would be only for the reception. For the services, dress as you would for church.
For clarification, the boots, skirt, and rope outfit was supposed to come across as sarcastic...I forget message boards can't convey tone very well. I wouldn't actually wear that, it's just what popped in my head when I read the invite. Sorry if it came across as what I was thinking of wearing.
For weddings or church: dark jeans, long-sleeve pearl snaps, vests, possibly bolos, black cowboy hats/boots for men. Also maybe Western suit jackets , depending on the season. For women, a nice dress is preferable; dark jeans and boots may be ok.
For really casual, lighter jeans, white hats, short-sleeved or sleeveless shirts. And or flannels and Carhartts for men. You can definitely get away with jeans here.
ETA: when in doubt, go for black accessories and dark wash, especially men. White hats and light blue denim are considered much less formal and may look inappropriate. A pretty dress that's easy to move in should be fine for you.
Honestly, the more I think about this term, the more it irritates me. It sounds too much like an outsider who doesn't understand rural Western living trying to be cutesy and mostly just being uninformative/borderline offensive. There is a dress code for special events in such areas, but it's not as commonly known.
"Love is the one thing we're capable of perceiving that transcends time and space."
The ceremony involves the boy/s or girl/s being called up to witness, or actually do, a reading from the Torah during a religious service. It is a rite of passage that signifies attaining adulthood.
Honestly, if you're outside of a traditional 'country' state, this kind of thing really looks like they want you to wear a costume more than anything else.
Same goes for hats, belts, shirts, and jeans. Dress jeans are always dark, and always starched, the heavier the better. Pearl snaps are the dressiest shirts.
This is pretty much how I expect most locals to dress for our wedding. For out of towners, I don't think I'll bother unless they have a specific question about where the line is on wearing something like jeans or boots, because it's not really who they are and what will make them comfortable. I'll just say it's outside and let them dress themselves.