The state or quality of being careless and not paying attention to danger or consequences.
From 'heedless' plus the noun suffix '-ness,' creating an abstract noun describing the quality of being heedless.
Many tragic stories feature 'heedlessness' as a character flaw—it's the word philosophers and writers use when someone had all the information but ignored it anyway.
Complete word intelligence in one call. Free tier — 50 lookups/day.