The phrase "unprofessional language" means using words or speech that is not appropriate or suitable for a professional setting or situation. Full definition
If you use unprofessional language reader may think that your resume is an unprofessional resume and there is a chance of not considering your resume for the further levels. (resumeformat.org)
When writing your resume, it is important that you watch out for common mistakes such as unprofessional language and spelling errors. (resume-now.com)
This raises the question of why the AFT and NEA would insist on bargaining unprofessional language into contracts that most of their members then ignore. (educationnext.org)