Most dehiscent is a term used to describe the opening or splitting of a structure. Its antonym, least dehiscent, would describe something that is less prone to opening or splitting. This could refer to materials like wood or metal, which are less likely to split than something like clay or pottery, which are more fragile. In biology, the term could refer to a plant or fruit that is less likely to burst open to release its seeds. Overall, the antonym of most dehiscent would describe something that is more durable, sturdy, and less prone to opening up or breaking apart.