stream - an output stream designator. The default is standard output.

For example, describe of a symbol might show the symbol's value, its definition, and each of its properties. describe of a float might show the number's internal representation in a way that is useful for tracking down round-off errors. In all cases, however, the nature and format of the output of describe is implementation-dependent.

describe can describe something that it finds inside the object; in such cases, a notational device such as increased indentation or positioning in a table is typically used in order to visually distinguish such recursive descriptions from descriptions of the argument object.

The actual act of describing the object is implemented by describe-object. describe exists as an interface primarily to manage argument defaulting (including conversion of arguments t and nil into stream objects) and to inhibit any return values from describe-object.

describe is not intended to be an interactive function. In a conforming implementation, describe must not, by default, prompt for user input. User-defined methods for describe-object are likewise restricted.