$TimedOut is a special symbol returned by certain functions when an operation times out.

Using Previous Results Defining Variables Values for Symbols

"How to" Topics Files, Streams, and External Operations Importing and Exporting

Everything Is an Expression The Meaning of Expressions Special Ways to Input Expressions

Your First Mathematica Calculations Arithmetic Defining Variables

The Main Loop Dialogs Date and Time Functions

Constructing Lists Manipulating Lists by Their Indices Nested Lists

Notebook Interfaces Doing Computations in Notebooks Notebooks as Documents

"How to" Topics Notebook Interface Input and Output in Notebooks

Why You Do Not Usually Need to Know about Internals Basic Internal Architecture The Algorithms of Mathematica