Definition
To compel a person by threats or intimidation to do something, surrender something, or abstain from something they would otherwise be entitled to do. In its legal sense, concuss describes the act underlying the civil and criminal wrong of concussion — a species of coercion achieved through fear rather than physical force. The term appears primarily in Scots law sources and in older civil-law influenced texts, where it denotes the use of unlawful threats (short of outright robbery) to extract money, property, or compliance from another.
Common Language
Modern common usage (Wiktionary): To injure the brain of, usually temporarily, by violent impact; also, secondarily, to force a person to do something by intimidation.
Historical common usage (Webster's 1913): To shake or agitate; to force a person to do or give up something by intimidation; to coerce.
The medical meaning — causing a concussion of the brain — has almost entirely displaced the coercive meaning in modern ordinary speech. A researcher encountering "concuss" in a legal text should resist the modern reflex toward the neurological sense. In historical legal sources, the word carries no physical-injury connotation whatsoever; it refers entirely to coercion through threatened harm, not harm itself.
Common Confusion
CONCUSS / CONCUSSION (legal) / CONCUSSION (medical): In contemporary general usage, "concussion" means traumatic brain injury. In historical legal usage — particularly Scots law and civil-law derived systems — "concussion" is a distinct wrong: the extraction of money or advantage by threats or intimidation, cognate to extortion. The act of committing that wrong is to concuss. A researcher using full-text search across historical legal corpora must be alert to this divergence; the medical and legal senses of the word family coexist in post-19th-century sources and context is the only reliable guide.
CONCUSS / EXTORT: The acts overlap substantially. Extortion in common law typically involves the unlawful taking of property under color of office or by threatened force. Concuss (and its noun concussion) more specifically captures coercion by fear of personal violence, false accusation, or other threatened injury — without necessarily involving an official actor. The distinction matters when tracing the genealogy of extortion doctrine through civil-law and Scots law sources.
Why It Matters in Research
This term is a minor but revealing node in the history of coercion doctrine. It appears in Scots law materials and in treatises drawing on Roman and civil-law sources, where the noun "concussion" (concussio) was a recognized category of civil wrong. Researchers tracing the development of extortion, duress, or economic coercion through comparative or historical sources will encounter it in that context.
The navigational trap is obvious: full-text corpus searches on "concuss" or "concussion" across Law Mind's holdings will return both the legal coercion sense and — in later materials — the medical sense. Narrowing searches to pre-1850 legal texts, or to Scots law and civil-law commentary specifically, will reduce noise. Burrill's citation to Shaw's Reports (Shaw's R. 322) is the kind of jurisdictionally specific anchor that confirms you are in the Scots law vein of the doctrine.
The term rarely appears in English common law materials as a term of art. If you find it in an English source, it is likely either a civil-law borrowing by a comparativist author or a general usage meaning coerce. It does not carry the technical weight in English law that it does in Scots law.
Researchers interested in the conceptual precursors of modern duress and extortion doctrine — particularly the civil-law tradition's treatment of metus (fear) as a vitiating factor in contracts and a basis for a personal action — should treat concuss and concussion as entry points into that literature.
Historical Dictionary Support
Black's Law Dictionary and Burrill's Law Dictionary are in precise agreement: both confine the legal definition to Scots law and define it simply as "to coerce." Burrill adds the Latin root (concutere, to shake violently) and the case citation to Shaw's Reports, which Black's omits. Neither source attempts to distinguish concuss from extortion or duress in any developed way, and neither acknowledges the medical meaning — reflecting the state of usage at the time of their composition, when the neurological sense had not yet dominated.
What the historical dictionaries do not do is situate the term within Roman law's actio quod metus causa, the civil action available to one who was compelled by fear to enter a transaction. That connection — between concussio, metus, and the broader doctrine of coercion — is available in civil-law treatises and comparative legal scholarship rather than in these dictionary sources. Researchers should not expect the dictionary entries alone to unlock the doctrinal depth; the entries are signposts, not the destination.
Jurisdictional Note
Concuss as a legal term of art is essentially confined to Scots law and civil-law influenced systems. It does not appear as a recognized term in English common law or in American legal usage with any technical legal meaning. Researchers working in jurisdictions with civilian heritage — Louisiana, Quebec, South Africa, Scotland — are most likely to encounter it in primary materials.
Encyclopedia Cross-Reference
Law Mind Encyclopedia: EXTORTION; DURESS