regionalPhysically unobstructed, uncovered, etc.

• an open winter
• He desires me to tell you that the present open weather induces him to accept Mr Vernon's invitation to prolong his stay in Sussex that they may have some hunting together.

Able to be used or interacted with in some way.

• Your bank account is now open.
• Phone lines open at 10 pm.

Able to be used or interacted with in some way.

• Banks are not open on bank holidays.

Able to be used or interacted with in some way.

• I hereby declare this fete open.
• The school has an open day on Saturday.

Able to be used or interacted with in some way.

• I am open to new ideas.
• Wherefore if Demetrius […] have a matter against any man, the law is open and there are deputies.

Able to be used or interacted with in some way.

• open to question; open to attack; open to criticism
• The service that I truly did his life, / Hath left me open to all injuries.

computingengineeringmathematicsAble to be used or interacted with in some way.

• I couldn't save my changes because another user had the same file open.

computingengineeringmathematicsAble to be used or interacted with in some way.

• You're getting short of memory because you have too many apps open.

Not hidden or restricted.

• The U.S. recognizes Canadian sovereignty over the islands bordering the passage but insists that the passage itself is an international waterway open to ships of all nations.

Not hidden or restricted.

• It is a blatant example of open criminality.
• His thefts were too open.

Not hidden or restricted.

• Nowadays people are more open about their sexuality.
• 1731-1735, Alexander Pope, Moral Essays with aspect open, shall erect his head

Not hidden or restricted.

• He published an open letter to the governor on a full page of The New York Times.

lawNot hidden or restricted.

• You will observe that this is an open letter and we reserve the right to mention it to the judge should the matter come to trial.

Not hidden or restricted.

• We hope that all aspects of the project will be open rather than paywalled.

computingeducationengineeringNot hidden or restricted.

• Since the launch early last year of […] two Silicon Valley start-ups offering free education through MOOCs, massive open online courses, the ivory towers of academia have been shaken to their foundations. University brands built in some cases over centuries have been forced to contemplate the possibility that information technology will rapidly make their existing business model obsolete.

hobbieslifestylesportsNot hidden or restricted.

gameshobbieslifestyleNot hidden or restricted.

• Compared to their last match, which was a dour and defensive affair, this was a very open game.

Not completed or finalised.

• an open question
• to keep an offer or opportunity open

businessNot completed or finalised.

• I've got open orders for as many containers of red durum as you can get me.

Not completed or finalised.

• an open curve, an open circuit

businesselectrical-engineeringelectricityNot completed or finalised.

graph-theorymathematicssciencesNot completed or finalised.

human-scienceslinguisticsphoneticsNot completed or finalised.

human-scienceslogicmathematicsHaving a free variable.

mathematicssciencestopologyWhich is part of a predefined collection of subsets of X, that defines a topological space on X.

entertainmentlifestylemusicOf a note, played without pressing the string against the fingerboard.

entertainmentlifestylemusicOf a note, played without closing any finger-hole, key or valve.

human-scienceslinguisticsphoneticsUttered with a relatively wide opening of the articulating organs; said of vowels.

• "Supposing somebody sees you, with all those flowers too? Supposing somebody writes him a letter? Ooooh!" (a pure round open Tamil O.)

human-scienceslinguisticsphoneticsUttered, as a consonant, with the oral passage simply narrowed without closure.

computingengineeringmathematicsSource code of a computer program that is not within the text of a macro being generated.

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.

hobbieslifestylesportsOf a club, bat or other hitting implement, angled upwards and/or (for a right-hander) clockwise of straight.

To cause or allow a gap to form or widen.

• Mudchester Rovers opened a sizeable lead on their rivals.
• A link opened under the strain, and the chain came apart.

businesselectrical-engineeringelectricityTo cause or allow a gap to form or widen.

To make or become available for use or interaction.

• He opened a secret bank account in Switzerland.
• We're opening the phone lines in ten minutes.

To make or become available for use or interaction.

• I will open the shop an hour early tomorrow.
• The summer fete was opened by the mayor.

To make or become available for use or interaction.

• Reading this book will open you to new ideas.
• This policy will open the government to criticism.

computingengineeringmathematicsTo make or become available for use or interaction.

• I can't open the file because someone else is editing it.

To make or become available for use or interaction.

• Please open the lights, the (electric) fan, the TV.

To start or begin.

• The show was opened by a terrible Elvis impersonator.
• Our band opened, and they came on second.

To start or begin.

• Our band opened for Nirvana.

To start or begin.

• The meeting opened with a statement from the chairman.

To start or begin.

• I don't want to open that subject.

To start or begin.

• to open a discussion
• to open fire upon an enemy

computingengineeringmathematicsTo start or begin.

• Click this icon to open Microsoft Word.

ball-gamescricketgamesTo start or begin.

card-gamespokerTo start or begin.

• After the first two players fold, Julie opens for $5.

To make an open relationship or marriage, i.e., with possible additional relationships.

• He assured me, unequivocally, that he was, and that he rather enjoyed the side benefits of my trysts: I was happier and living more honestly, as well as off his back about many of the issues that had been troublesome for me before we opened our relationship.
• I wouldn’t do it unless there is a reason for it, I wouldn’t open a marriage just for fun. I think it’s too dangerous. I know I’m a monogamous type of person—I like just one person at a time; actually sleeping with more than one person in separate relationships is too confusing.

obsoleteTo disclose; to reveal; to interpret; to explain.

• The king opened himself to some of his council, that he was sorry for the earl's death.
• Unto thee have I opened my cause.