One-use item

From IFWiki

A one-use item is a portable object in a game which only serves one useful game purpose, forming the solution (or part of the solution) to a single puzzle. The paradigm of one-use items is a key that will only unlock one door - a realistic enough behaviour. But excessive reliance on one-use items can make a game inflexible, tedious or unfair - particularly if they are objects which a player might reasonably expect to have multiple uses.

One-use items are not strictly speaking incompatible with multiple solutions, but one-use items are strongly associated with single-solution puzzles.