A large flat surface, finished with black slate or a similar material, that can be written upon with chalk and subsequently erased; a chalkboard.
To use a blackboard to assist in an informal discussion.
A thin, flat, circular plate or similar object.
A disc - either a CD-ROM, an audio CD, a DVD or similar removable storage medium.
A ring- or cup-shaped enlargement of the flower receptacle or ovary that bears nectar or, less commonly, the stamens.
Something resembling a disk.
A type of harrow.
An intervertebral disc
To harrow.
To move towards, or operate at, zero blade pitch, orienting the propeller blades face-on to the oncoming airstream and maximising the drag generated by the propeller.