Definitions from Wiktionary ( )

▸ adjective:  (usually not comparable) Not closed.
▸ adjective:  Able to be accessed (physically).
▸ adjective:  Able to have something pass through or along it.
▸ adjective:  (of a body part) Not covered; showing what is inside.
▸ adjective:  (of a sandwich, etc.) Composed of a single slice of bread with a topping.
▸ adjective:  Not physically drawn together, closed, folded or contracted; extended.
▸ adjective:  (not comparable) Actively conducting or prepared to conduct business.
▸ adjective:  (comparable) Receptive.
▸ adjective:  (not comparable) Public
▸ adjective:  (not comparable) With open access, of open science, or both.
▸ adjective:  (not comparable) Candid, ingenuous, not subtle in character.
▸ adjective:  (now regional) Mild (of the weather); free from frost or snow.
▸ adjective:  (mathematics, logic, of a formula) Having a free variable.
▸ adjective:  (mathematics, topology, of a set) Which is part of a predefined collection of subsets of X, that defines a topological space on X.
▸ adjective:  (graph theory, of a walk) Whose first and last vertices are different.
▸ adjective:  (computing, not comparable, of a file, document, etc.) In current use; connected to as a resource.
▸ adjective:  (engineering, gas and liquid flow, of valve or damper) To be in a position allowing fluid to flow.
▸ adjective:  (electricity, of a switch or circuit breaker) To be in a position preventing electricity from flowing.
▸ adjective:  (sometimes business) Not fulfilled or resolved; incomplete.
▸ adjective:  Not settled or adjusted; not decided or determined; not closed or withdrawn from consideration.
▸ adjective:  (music, stringed instruments) Of a note, played without pressing the string against the fingerboard.
▸ adjective:  (music) Of a note, played without closing any finger-hole, key or valve.
▸ adjective:  Not of a quality to prevent communication, as by closing waterways, blocking roads, etc.; hence, not frosty or inclement; mild; used of the weather or the climate.
▸ adjective:  (law, of correspondence) Written or sent with the intention that it may made public or referred to at any trial, rather than by way of confidential private negotiation for a settlement.
▸ adjective:  (phonetics) Uttered with a relatively wide opening of the articulating organs; said of vowels.
▸ adjective:  (phonetics) Uttered, as a consonant, with the oral passage simply narrowed without closure.
▸ adjective:  (phonetics, of a syllable) That ends in a vowel; not having a coda.
▸ adjective:  (computing, education) Made public, usable with a free licence and without proprietary components.
▸ adjective:  (medicine) Resulting from an incision, puncture or any other process by which the skin no longer protects an internal part of the body.
▸ adjective:  (computing, used before "code") Source code of a computer program that is not within the text of a macro being generated.
▸ adjective:  (of a multi-word compound) Having component words separated by spaces, as opposed to being joined together or hyphenated; for example, time slot as opposed to timeslot or time-slot.
▸ verb:  (transitive) To make something accessible or allow for passage by moving from a shut position.
▸ verb:  (transitive) To make (an open space, etc.) by clearing away an obstacle or obstacles, in order to allow for passage, access, or visibility.
▸ verb:  (transitive, intransitive, engineering, gas and liquid flow, of valve or damper) To move to a position allowing fluid to flow.
▸ verb:  (transitive, intransitive, electricity, of a switch, fuse or circuit breaker) To move to a position preventing electricity from flowing.
▸ verb:  (Manglish, Philippines) To turn on; to switch on.
▸ verb:  (transitive) To bring up, broach.
▸ verb:  (transitive) To enter upon, begin.
▸ verb:  (transitive) To spread; to expand into an open or loose position.
▸ verb:  (transitive) To make accessible to customers or clients.
▸ verb:  (transitive) To start (a campaign).
▸ verb:  (intransitive) To become open.
▸ verb:  (intransitive) To begin conducting business.
▸ verb:  (intransitive) To perform before others at a concert or show.
▸ verb:  (intransitive, cricket) To begin a side's innings as one of the first two batsmen.
▸ verb:  (intransitive, poker) To bet before any other player has in a particular betting round in a game of poker.
▸ verb:  (transitive, intransitive, poker) To reveal one's hand.
▸ verb:  (computing, transitive, intransitive) To connect to a resource (a file, document, etc.) for viewing or editing.
▸ verb:  (transitive, nursing) To make (a bed) ready for a patient by folding back the bedcovers.
▸ verb:  (obsolete) To disclose; to reveal; to interpret; to explain.
▸ noun:  (in the definite) Open or unobstructed space; an exposed location.
▸ noun:  (in the definite) Public knowledge or scrutiny; full view.
▸ noun:  (electronics) A defect in an electrical circuit preventing current from flowing.
▸ noun:  A sports event in which anybody can compete.
▸ noun:  The act of something being opened, such as an e-mail message.

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