1. A kind of symbolic diagram (used in chemistry, mathematics, etc.) in which a system of connexions is expressed by spots or circles, some pairs of which are colligated by one or more lines. Also, occasionally the system expressed by one of these diagrams.
2. In medicine, a line or tracing denoting varying values of commodities, temperatures, urinary output, etc.; more generally, any geometric or pictorial representation of measurements that might otherwise be expressed in tabular form.
3. An apparatus of the nature of the chromograph, hectograph, etc., for taking copies of writing by pressing it on a gelatinous surface.
4. In philology, a visual symbol representing a phoneme or a segment or feature of speech; especially, a letter, or one of its occurrent forms, or a combination of letters.