1.Definition: (of textures) full of small openings or gaps
"An open texture"
2.Definition: (set theory) of an interval that contains neither of its endpoints
3.Definition: accessible to all
"Open season", "An open economy"
4.Definition: affording free passage or access
"Open drains", "The road is open to traffic", "Open ranks"
5.Definition: affording free passage or view
"Open waters", "The open countryside"
6.Definition: affording unobstructed entrance and exit; not shut or closed
"An open door", "They left the door open"
7.Definition: having no protecting cover or enclosure
"An open boat", "An open fire", "Open sports cars"
8.Definition: not brought to a conclusion; subject to further thought
"An open question"
9.Definition: not defended or capable of being defended
"An open city", "Open to attack"
10.Definition: not having been filled
"The job is still open"
11.Definition: not requiring union membership
"An open shop employs nonunion workers"
12.Definition: not sealed or having been unsealed
"The letter was already open", "The opened package lay on the table"
13.Definition: open and observable; not secret or hidden
14.Definition: open to or in view of all
"An open protest", "An open letter to the editor"
15.Definition: openly straightforward and direct without reserve or secretiveness
"An open and trusting nature"
16.Definition: possibly accepting or permitting
"Open to interpretation", "An issue open to question"
17.Definition: ready for business
"The stores are open"
18.Definition: ready or willing to receive favorably
19.Definition: used of mouth or eyes
"Keep your eyes open", "His mouth slightly opened"
20.Definition: with no protection or shield
"Open to the weather", "An open wound"
21.Definition: without undue constriction as from e.g. tenseness or inhibition
"The clarity and resonance of an open tone", "Her natural and open response"