What word describes a rupture, gap, or hole?

The term that best describes a rupture, gap, or hole is 'breach.' This word is commonly used in various contexts, such as in legal, security, or physical situations, to indicate a violation or breaking of something that is normally intact. When referring to a physical space, a breach signifies an opening or break in a barrier, which perfectly aligns with the concept of a rupture or gap.

The other terms, while related to breaks or separations, generally carry different connotations. For instance, 'fissure' often refers to a narrow opening or crack, typically in geological contexts. 'Break' is a more generic term that signifies any separation but lacks the specificity of a gap or hole. 'Crack' usually indicates a fracture or fissure that is less pronounced than a breach, often implying a smaller or less significant opening. Therefore, 'breach' is the most appropriate choice for describing a rupture, gap, or hole, as it encompasses a more substantial and definitive separation.