General:
* Mass-produced: This emphasizes the opposite of high-fashion's exclusivity and handmade nature.
* Ready-to-wear: This refers to clothing made in standard sizes and readily available for purchase, unlike the bespoke nature of couture.
* Off-the-rack: Similar to "ready-to-wear," this term highlights the mass production aspect.
Specific:
* Informal: If "couture" refers to formal wear, "informal" could be an antonym.
* Casual: Similar to "informal," this emphasizes a relaxed and everyday style.
* Basic: This suggests simplicity and lack of elaborate design, as opposed to couture's intricate details.
The best antonym will depend on the specific context and the nuance you want to convey.