site space hole http://id.loc.gov/authorities/subjects/sh85061447 http://purl.obolibrary.org/obo/NCIT_C124640 http://semanticscience.org/resource/SIO_000660 https://en.wikipedia.org/wiki/Category:Holes https://en.wikipedia.org/wiki/Hole https://www.wikidata.org/wiki/Q20204151 An aperture or hollow space within a solid mass. holes