otherwise inaccessible part: n. (of an object, O1)
an object, O2, which would be made inaccessible if
O1 were made inaccessible. (Every object is an
otherwise inaccessible part of itself.)
output: adj. (of a stream)
supporting output operations (i.e., being a "data sink").
An output stream might also be an input stream,
in which case it is sometimes called a bidirectional stream.
See the function output-stream-p.