Definition
In maritime law, the striking of a moving vessel against a stationary object — a fixed pier, a moored ship, a reef, or similar immovable structure. The vessel in motion is the alliding vessel; the object struck is passive.
Allision is formally distinguished from collision, in which two vessels are both in motion when they make contact. The practical importance of this distinction lies in causation and liability analysis: when one party is stationary, fault is more readily attributed to the moving vessel, and the navigation rules governing fault allocation differ accordingly.
Common Language
Modern common usage (Wiktionary): "The striking of a vessel against a fixed object; the act of alliding or an instance thereof. The act of dashing against or striking upon."
Historical common usage (Webster's 1913): "The act of dashing against, or striking upon. The boisterous allision of the sea."
The common meaning is broad — any forceful contact between objects — while the legal meaning is narrow and technical, confined to maritime law and specifically defined by the fixed or stationary nature of the object struck. In general usage, allision and collision are interchangeable; in admiralty law, they are not.
Common Confusion
ALLISION vs. COLLISION: These terms are frequently conflated in both historical sources and modern usage, including by courts. The technical distinction — allision involves a moving vessel and a fixed object; collision involves two moving vessels — is well established in admiralty doctrine but inconsistently applied. Bouvier notes the confusion directly, observing that "collision is used to denote cases strictly of allision." Researchers should not rely on the term used in a source to determine the actual fact pattern; read the underlying facts.
Why It Matters in Research
This is a navigational term as much as a legal one, and the distinction between allision and collision carries doctrinal weight in admiralty cases involving fault, burden of proof, and limitation of liability. Courts applying the Pennsylvania Rule (which shifts the burden to a vessel in violation of a statutory rule at the time of a maritime accident) may apply it differently depending on whether the incident is characterized as an allision or a collision.
In historical sources, the distinction is unreliable. Bouvier explicitly acknowledges that the two terms are not carefully observed. Researchers working with 19th-century admiralty records, shipping reports, or insurance documents should treat "collision" in those sources as potentially encompassing what modern doctrine would call allision. Conversely, modern maritime law reporters and treatises are more likely to apply the distinction precisely.
The term appears almost exclusively in admiralty and maritime law contexts. It is not a term of art in common law tort, contract, or any land-based legal framework. Researchers encountering it outside a maritime context should treat it as loose usage.
Historical Dictionary Support
The historical dictionaries largely agree on the core definition but vary in how much weight they place on the collision distinction.
Burrill provides the most complete treatment, defining allision as "a striking against; the running of one vessel against another" while noting the distinction from collision as the running of two vessels against each other or a striking together. Burrill cites Jacobsen's Sea Laws, one of the foundational treatises of maritime law, lending authority to the distinction.
Rapalje & Lawrence reach the same result and usefully supply the Latin root (ad + lædere, to dash against), clarifying that the term signals a directional, one-sided impact rather than a mutual encounter.
Black's (both editions) defines allision briefly as "the running of one vessel into or against another, as distinguished from a collision." The phrasing "into or against another" is slightly imprecise — it does not make clear that the other vessel must be stationary — but the distinction from collision is preserved.
Bouvier is the most candid: he flags that the distinction between allision and collision is "not very carefully observed," which is historically accurate and a useful warning for researchers.
Anderson's Dictionary of Law offers only a cross-reference to Collision, treating allision as a subordinate term — a reasonable editorial choice given the overlap in usage.
None of the historical dictionaries address the burden-shifting consequences that modern admiralty doctrine attaches to the allision/collision distinction. That doctrinal development postdates or is simply outside the scope of the dictionary literature.
Jurisdictional Note
Allision is a term of federal admiralty and maritime law in the United States. Admiralty jurisdiction is vested in the federal courts under Article III of the Constitution, and the substantive rules governing vessel fault and liability are federal in character. State law plays a limited role. Researchers in other common law jurisdictions will find similar terminology in English admiralty practice, though usage in specific rules of navigation may differ.