What does sniffer mean?
A “sniffer” most commonly means an informant who supplies information to police or another authority. The word can also denote a person, device, or animal trained to detect particular scents or substances, such as drugs, explosives, or leaking gas; sniffer dogs are a familiar example. As a verb, “sniffer” means to investigate or search for something, often discreetly or unofficially, and usually appears in the phrase “sniff out.” Its implications vary by context. The informant sense may carry an informal or potentially disparaging tone, while the detection sense is often technical and neutral. Although the verb “sniffer” exists, “sniff” or “sniff out” is more common in everyday English. The word is useful because it joins the ideas of searching, detecting traces, and uncovering hidden information.
A person who provides information to police or another authority, especially as an informant.
"The sniffer agreed to testify in return for protection."
Often informal and sometimes viewed as disparaging; “informant” is a more neutral alternative.
A person, animal, or device trained or designed to detect particular scents or substances.
"The sniffer detected traces of the chemical within minutes."
Common in technical and law-enforcement contexts, especially with trained dogs and devices designed to detect drugs, explosives, or gas.
To investigate or search for something, especially in an unofficial or covert manner.
"Reporters sniffed out several inconsistencies in the account."
Chiefly informal and most natural in the phrase “sniff out.”
The plural is used for multiple informants, people, devices, or animals that perform a sniffing or detection function.
"Several sniffers were placed around the perimeter of the building."
A sniffer dog can follow a trail of scent so faint that people cannot detect it themselves.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does sniffer come from?
The word derives from English “sniff,” which is of imitative origin and is associated with drawing air through the nose to detect a scent. “Sniffer” developed from this verb in the sense of one who or that which sniffs, and its use for an informant arose from the figurative idea of “sniffing out” information or wrongdoing.
Related word forms
How sniffer is actually used
As a noun, “sniffer” is often informal when referring to an informant. As a verb, it is chiefly informal and commonly occurs in the expression “sniff out.” The noun is also used technically for devices or animals trained to detect particular substances or scents.