Because K-12 teachers have access to private educational data, they are increasingly at risk of being affected by cybersecurity threats. Examining how teachers conceptualize cybersecurity is vital so that cybersecurity training can be tailored to teachers' understanding of cybersecurity. This study examined K-12 teachers' (n = 255) personalized definitions of cybersecurity as these perceptions may influence online behaviors. These definitions were also reviewed by teacher type (cybersecurity teacher or noncybersecurity teacher), teacher self-identified gender, and teacher age. The cybersecurity definitions were aligned and contextualized within a modified NICE Framework Core with a specific focus on three areas: protection and monitoring, response and mitigating threats, and improvement and communication. Teacher responses were thematically coded and analyzed. Results showed that K-12 teachers, regardless of if the teacher taught cybersecurity, defined cybersecurity as a 1) skill and/or a 2) source of protection while involved in online experiences. When examined by gender and age cohorts, descriptions between groups were similar. The theme of improvement and communication was the least represented among K-12 teachers' definitions of cybersecurity. As perceptions and definitions of cybersecurity may influence online behavior, teachers' conceptualization of cybersecurity may assist in how training opportunities are designed and implemented for teachers to encourage safe and responsible online behavior for the school community.