What does flatfoot mean?
Flatfoot refers to a common foot condition in which the arch of the foot has collapsed, so that the entire sole makes contact with the ground while standing. Medically known as pes planus, it may be present from childhood or develop later through injury, aging, obesity, or prolonged standing, and it can cause pain in the feet, ankles, knees, and lower back — though many people with flat feet experience no symptoms at all. The word also has an informal second life in American slang, where a "flatfoot" is a policeman, a nickname dating to an era when officers spent long hours walking city beats, supposedly flattening their arches. In modern usage the medical meaning dominates and appears in clinical and everyday contexts alike, while the slang term now sounds distinctly old-fashioned, evoking black-and-white detective films more than contemporary policing.
A condition in which the arch of the foot is collapsed, causing the whole sole to rest on the ground; a foot having this condition.
"The army physical found flatfoot in his left foot and disqualified him."
The plural is irregular: "flatfeet." The clinical term is pes planus.
Informal, chiefly American: a police officer, especially one assigned to walk a beat.
"A couple of flatfeet showed up to break up the argument."
Somewhat dated and jocular in tone.
Because the head noun "foot" forms its plural irregularly, the plural of flatfoot is "flatfeet," not "flatfoots." This applies to both the medical and slang senses.
"Flatfeet are common in infants and usually resolve as the arch develops."
Before radios and patrol cars, American cops walked their beats all day until their arches collapsed — which is exactly how they picked up the nickname "flatfoots."
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of flatfoot
Flatfoot is a straightforward English compound formed from "flat" and "foot," first recorded in the nineteenth century to describe the anatomical condition of a fallen arch. The compound follows a productive Germanic pattern of pairing an adjective with the native word "foot," whose Old English ancestor "fōt" also gives us everyday terms like footprint, footwear, and barefoot. The American slang sense for a policeman emerged in the early twentieth century, reportedly among officers themselves before spreading into popular usage.
Related word forms
How flatfoot is actually used
In the medical sense, "flatfoot" is standard clinical vocabulary (the adjective form "flatfooted" also describes someone caught unprepared, especially in sports commentary). The slang sense for a policeman is informal, somewhat dated, and largely American; it carries a mildly derogatory or jocular tone.
Easily confused with flatfoot
"Flat-footed" is an adjective meaning unprepared (as in "caught flat-footed") or walking flatly, whereas "flatfoot" is the noun for the foot condition or, in slang, a policeman.