Most nonnative can be described as something or someone who is not native or indigenous to a particular place or region. Antonyms for this phrase could include 'native', 'indigenous', 'local', 'natural', 'homegrown', or 'original'. These words imply a close association or link with a particular location, as opposed to being foreign or alien. For example, instead of saying 'most nonnative plants', one could use the term 'native species' to refer to plants that are indigenous to a specific region. Similarly, instead of 'most nonnative residents', one could use 'locals' to describe people who were born and raised in a particular area.