You would say semi formal, which means dressy/casual.
The word attire refers to clothing, formal or dressy in particular.
slacks with a collared shirt or even a sport coat
wear a dressy short sleeve polo and some dressy pants...thts not only casual but its not too fancy and wont get you hot.
Dressy casual (no shorts and no open toed shoes) up to three piece suits.
lady: dressy blouse and slacksman great pair of pants and smart shirt open at the collar (no tie)or maybe just nice jeans and a nice button down
Business cocktail attire is a step above what you would wear to work, as far as being dressier. However, it is not as flashy as typical cocktail attire. The clothing should be dressy, but conservative for both males and females.
Something by the designer, of depending on the scale of the show dressy casual to cocktail formal attire.
In most setting dressy carpi pant suits work as semi-formal attire. If you are in doubt check with the host or venue for guidance.
I would think smart trousers, but not jeans with a trendy shirt and jacket. No trainers. And certainly no tie, or bow tie
A smart casual dress code is typically an informal but neat attire. It is not as dressy as a formal dress code but it is a step up from business casual.
Smart casual attire for men means wearing informal but neat attire. It is not as dressy as formal attire but a step up from business casual. The attire includes shirts with collars, jeans or khaki trousers, and loafers or other closed shoes.