open

Not closed

Not physically drawn together, closed, folded or contracted; extended

“an open hand; an open flower”

Actively conducting or prepared to conduct business.

“Banks are not open on bank holidays.”

Receptive.

“I am open to new ideas.”

Public

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

Candid, ingenuous, not subtle in character.

“The man is an open book.”

(of a formula) Having a free variable.

(of a set) Which is part of a predefined collection of subsets of X, that defines a topological space on X.

(of a walk) Whose first and last vertices are different.

(of a file, document, etc.) In current use; mapped to part of memory.

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

Not fulfilled.

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

Not settled or adjusted; not decided or determined; not closed or withdrawn from consideration.

“an open question”

(stringed instruments) Of a note, played without pressing the string against the fingerboard.

(wind instruments) Of a note, played without closing any finger-hole, key or valve.

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.

“an open winter”

(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. (Opposite of "without prejudice")

“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.”

Uttered with a relatively wide opening of the articulating organs; said of vowels.

Uttered, as a consonant, with the oral passage simply narrowed without closure.

(of a syllable) That ends in a vowel; not having a coda.

Made public, usable with a free licence and without proprietary components.

Resulting from an incision, puncture or any other process by which the skin no longer protects an internal part of the body.

To make something accessible or allow for passage by moving from a shut position.

“Turn the doorknob to open the door.”

To make (an open space, etc.) by clearing away an obstacle or obstacles, in order to allow for passage, access, or visibility.

“He opened a path through the undergrowth.”

To bring up, broach.

“I don't want to open that subject.”

To enter upon, begin.

“to open a case in court, or a meeting”

To spread; to expand into an open or loose position.

“to open a closed fist”

To make accessible to customers or clients.

“I will open the shop an hour early tomorrow.”

To start (a campaign).

“Vermont will open elk hunting season next week.”

To become open.

“The door opened all by itself.”

To begin conducting business.

“The shop opens at 9:00.”

To begin a side's innings as one of the first two batsmen.

To bet before any other player has in a particular betting round in a game of poker.

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

To reveal one's hand.

“Jeff opens his hand revealing a straight flush.”

(of a file, document, etc.) To load into memory for viewing or editing.

To disclose; to reveal; to interpret; to explain.

(with the) Open or unobstructed space; an exposed location.

“I can't believe you left the lawnmower out in the open when you knew it was going to rain this afternoon!”

(with the) Public knowledge or scrutiny; full view.

“We have got to bring this company's corrupt business practices into the open.”

A defect in an electrical circuit preventing current from flowing.

“The electrician found the open in the circuit after a few minutes of testing.”

A sports event in which anybody can compete

“the Australian Open”