If you're looking for a word that sounds similar, it could be a misspelling of one of these:
* Pliable: meaning easily bent or molded.
* Plight: meaning a dangerous, difficult, or unfortunate situation.
* Plies: meaning layers, often used in the context of fabrics or rope.
If you could provide more context about where you saw or heard "pliest," it might be easier to figure out what was intended.