A breakwater.
A defensive wall or rampart.
A defense or safeguard.
Any means of defence or security.
The planking or plating along the sides of a nautical vessel above her gunwale that reduces the likelihood of seas washing over the gunwales and people being washed overboard.
To fortify something with a wall or rampart.
To provide protection of defense for something.
A gap permitting passage through.
The first few measures of a musical composition.
The first performance of a show or play by a particular troupe.
The initial period when a show at an art gallery or museum is first opened, especially the first evening.
A vacant position, especially in an array.
An unoccupied employment position.
In mathematical morphology, the dilation of the erosion of a set.
An act or instance of making or becoming open.
A time available in a schedule.
An opportunity, as in a competitive activity.
An act or instance of beginning.
The first few moves in a game.
Pertaining to the start or beginning of a series of events.
describing the first period of play, usually up to the fall of the first wicket; describing a batsman who opens the innings or a bowler who opens the attack