A piece of blotting paper in a pad as a piece of desk furniture.
A register of the related events made in the form of the list of times and brief descriptions.
A daily register of arrests and other events in a police station.
A portion of blotter acid.
A book in which notes or memoranda are written.
A kind of user interface in literate programming, allowing calculations to be interspersed with human-readable comments, diagrams, etc.