Which word would you associate with something small or below average size?

The choice of "diminutive" accurately captures the idea of something being small or below average in size. The term "diminutive" directly refers to an object or being that is notably smaller than usual. It is often used to describe people, animals, or objects that are cute or compact in stature, thereby emphasizing their smallness.

For instance, saying that a puppy is diminutive immediately conveys its small size, suggesting both a physical characteristic and an endearing quality.

The other terms do not relate to size in the same way. "Inexorable" refers to something that is relentless or unyielding. "Repast" pertains to a meal or the food served at a meal, which has no connection to size. "Poignant" describes something that evokes a keen sense of sadness or regret, again not relevant to the concept of size. Thus, "diminutive" is the most fitting word for describing something small or below average in size.