Frank and candidly straightforward / Generous and kind / Emotionally receptive

completely open / having no laws or law enforcement / unsettled or unresolved / vulnerable or unprotected / (sports) without the presence of opponents nearby

(grammar) A compound word with spaces in it, for example, high school, school bus, or science fiction.

A house habitually kept open to callers. / An event, often in one's home, at which there are few restrictions regarding who and how many may attend.

(sometimes attributive) Creative work that others can freely and legally copy or modify.

The regular times of day when a shop, office or similar is open to the public.

(computing) A system allowing hardware and software from different manufacturers to be used together seamlessly. / (physics) A system that can exchange both matter and energy with its surroundings.

A knifelike device with a blunt edge, used for slicing letters open.

(intransitive, cricket) To turn the face of the bat outwards in order to hit the ball on the off side.

Used other than figuratively or idiomatically: see open, attack: to begin attacking, to commence battle. / (cricket) Of a bowler: to bowl one of the first two overs.