The term 'police officer, slangily' can be summarized in two crossword solutions: 'COP' (3 letters) and 'FLATFOOT' (8 letters). 'COP' is a slang term for a police officer that has been used since the early 1900s. It is derived from the verb 'to COP', which means to seize or capture. 'FLATFOOT' is another slang term for a police officer that has been used since the late 1800s. It is derived from the idea of a police officer having feet that are flat from walking the beat.