1. A hole or small recess for pigeons to nest
2. A small open compartment (as in a desk or cabinet) for keeping letters or documents
3. A neat category which usually fails to reflect actual complexities
4. A small compartment in a desk or case for the keeping of letters, documents, etc.

1. To treat or classify according to a mental stereotype; SYN. stereotype, stamp.
2. To assign to an often restrictive category; classify