Inexcusable/ˌɪnɪkˈskjuːzəbl/ Definition 1 of 1Pro Tip 1/3Severity Level Use 'inexcusable' to express that something is extremely bad or serious. Leaving the child unattended was inexcusable. Pro Tip 2/3No Justification 'Inexcusable' implies that no excuse can justify the action or mistake. Cheating on the exam is inexcusable. Pro Tip 3/3Strong Disapproval The word conveys strong moral or ethical condemnation. The judge called the negligence inexcusable.