Which term describes the act of fusing or growing together?

The term that describes the act of fusing or growing together is "coalesce." This word comes from the Latin root "coalescere," which means to grow together or unite. In various contexts, coalesce can refer to physical entities, such as liquids merging into one, or abstract concepts, like ideas or groups coming together to form a unified whole. Its use conveys the idea of an amalgamation, blending, or synthesis, which aptly fits the definition provided in the question.

The other terms do not share this meaning. "Damp" refers to a slight wetness or moisture, not related to fusion or unity. "Compaisance" (likely meant to be "complacence") refers to a feeling of self-satisfaction, often without awareness of potential dangers or deficiencies, which is unrelated to the idea of joining or merging. "Contrite" describes a feeling of remorse or guilt, which does not pertain to the idea of coming together. Thus, "coalesce" is clearly the most appropriate choice in this context.