To begin operations; to set things in motion.

A morning on which an establishment (such as a school or business) is open to the public, allowing visitors to view the premises and learn about the operation of the organisation.

(idiomatic) To allow some action to proceed more swiftly or to a greater extent

simple past tense and past participle of open the floodgates

(now rare) Frank, unsecretive; not concealing one's feelings. / With the breast exposed; (of clothing) not covering the breast.

A verdict upon an inquest which finds that a crime has been committed without specifying the criminal.

(cricket) To be one of a pair of cricketers (batsmen) that start a side's innings, who are also known as the opening pair or openers.

simple past tense and past participle of open the batting

Used other than figuratively or idiomatically: see open, wide. / (idiomatic, intransitive) To open one's mouth wide, to gape

(transitive) To use a sudden, quick hand motion to open (something relatively small like a book, a lighter, etc.).