Drug repositioning studies in recent decades have revealed a growing number of antimicrobials effective at treating infection types tangential to their original antimicrobial classification. Such ‘pan-pathogen antimicrobials’ (or ‘broad-spectrum anti-infectives’) have not yet been formally characterised. This review examines historical limitations of the canonical antimicrobial lexicon in light of the contemporary model for infectious disease and propounds a taxonomy that defines antimicrobials according to the host-pathogen interactome, not the pathogen. By doing so, antimicrobials that are effective at treating multiple infection types are highlighted, namely azithromycin, ivermectin, niclosamide, and nitazoxanide. Recognition of the pan-pathogen nature of these antimicrobials can stimulate a more unified approach to antimicrobial development cognisant of generalised anti-infective mechanisms within the host-pathogen interactome and anticipatory of future pandemics and bioterrorist attacks.