Definition
OST is a Latin abbreviation appearing in historical English legal sources, shorthand for one of several Latin phrases beginning with "ost-" — most commonly encountered as an abbreviated form within manuscript and printed legal texts of the medieval and early modern periods. In legal usage, the abbreviation most frequently signals forms of the Latin verb ostendere (to show, to exhibit), appearing in procedural writs and pleading formulas that required a party to produce, exhibit, or show cause before the court.
The abbreviation surfaces in distinct procedural contexts:
1. As a shorthand for ostensurus (he being about to show), used in writ language commanding a party to appear and show why something should or should not be done — the structural ancestor of show-cause procedure.
2. As a fragment marker in manuscript copies of plea rolls and register-of-writs collections, where scribal economy condensed repeated Latin phrases to their opening letters.
Because Burrill's entry under OST redirects to related Latin ordinal terms (ordo agendi, ordo brevium) rather than defining OST independently, the abbreviation functioned less as a term of art with fixed meaning and more as a scribal convention whose referent must be reconstructed from surrounding text.
Common Language
Modern common usage (Wiktionary): OST is an initialism for "original soundtrack," referring to music composed or compiled for a film, television series, or video game.
Historical common usage (Webster's 1913): Webster's 1913 treats "ost" as a variant spelling pointing to "oast" — a kiln used for drying hops or malt — with no connection to legal usage.
The gap between common and legal meaning here is total rather than partial. Neither the modern media-industry initialism nor the agricultural implement has any relationship to the procedural Latin abbreviation found in historical legal sources. A researcher encountering OST in a digitized plea roll or writ collection will find no assistance from general dictionaries and must treat it as a context-dependent scribal abbreviation requiring Latin expansion.
Common Confusion
OST as a standalone abbreviation is easily confused with other Latin contractions of similar appearance in manuscript sources — particularly OSD (ostendendum, "to be shown") and the cluster of ORD- abbreviations (ordo, ordinatio) that Burrill catalogs in the same alphabetical range. The proximity of ordo agendi and ordo brevium in Burrill's own entries reflects this compression: legal dictionaries of the 19th century often grouped Latin abbreviations thematically rather than strictly alphabetically, making adjacent entries unreliable guides to a specific abbreviation's meaning. Researchers should not assume that OST in a given source refers to any single Latin phrase without consulting the full writ formula or plea roll context.
Why It Matters in Research
The primary research challenge with OST is disambiguation. Historical legal manuscripts used abbreviation systems that varied by scribe, period, and court — Chancery practice differed from Common Pleas, and both differed from ecclesiastical court usage. A string like "ost'" with a superscript mark of abbreviation in a 13th-century plea roll is not the same artifact as "OST" printed in a 19th-century digest or legal dictionary.
For Law Mind corpus researchers:
Burrill's treatment is thin. His entry does not define OST directly but instead cross-references Latin ordinal terms, suggesting he encountered the abbreviation in sources organized around procedural sequence (ordo) rather than exhibition (ostendere). This means Burrill's entry is more useful for understanding writ-ordering vocabulary than for decoding show-cause language.
Digital search traps are significant. Running OST as a keyword search across the Law Mind corpus will surface false positives from words containing the string (costs,host, most, posted) at very high rates. Researchers should search within Latin-language segments or use phrase-level search tied to writ formulas.
Ostensurus and its relatives are the productive thread. If the research question concerns show-cause procedure, the better entry points are the English-language entries for SHOW CAUSE, RULE TO SHOW CAUSE, and the writ forms collected under CERTIORARI and MANDAMUS, where the ostensurus formula appears in translated or explained form.
Scribal abbreviations in plea rolls are not standardized across the Law Mind corpus. If working from facsimile or transcription sources, cross-reference against a paleography guide for the relevant court and century before treating any OST expansion as settled.
Historical Dictionary Support
Burrill is the sole source dictionary for this entry, and his coverage is oblique. Rather than defining OST as an independent term, his entry for the alphabetical range surrounding it catalogs Latin procedural phrases — ordo agendi (the order of suing, citing Fleta, lib. 5, c. 6, § 8), ordo brevium (the order of writs, citing Fleta, lib. 5, c. 6, § 31), and ordo curiae (an order of a court, citing 1 Rep. in Ch. 55). This clustering suggests that Burrill organized his Latin abbreviation entries by the procedural family to which they belonged rather than by strict alphabetical expansion. The effect for modern researchers is that Burrill's dictionary is more useful as a guide to the conceptual neighborhood of a term than as a precise decoder of any specific abbreviation.
No other historical dictionaries in the Law Mind corpus — not Black's, not Bouvier, not Tomlin's — carry a standalone OST entry, which itself signals that the abbreviation was understood by practitioners as transparent shorthand rather than a term requiring definition.
Jurisdictional Note
OST as a Latin scribal abbreviation is a feature of English common law manuscript tradition and the courts that inherited or modeled themselves on it. American legal sources after the colonial period rarely use the abbreviation; researchers working in post-Revolutionary American materials are unlikely to encounter it except in direct quotations from English precedent.
Encyclopedia Cross-Reference
See Law Mind Encyclopedia — WRITS (historical writ forms and Latin procedural language); PLEADING (historical) (development of show-cause and rule procedure).