Definition: A boolean attribute in XHTML is an attribute that is either on or off. If the attribute is present, it takes effect, otherwise it does not. In valid XHTML, all attributes must have a value, so boolean attributes are written boolean="boolean". For example <option value="test" selected="selected">test</option>
Pronunciation: bu lee an - (adjective)
Examples: In the option tag, selected is a boolean attribute:
<option value="test" selected="selected">test</option>
<option value="test" selected="selected">test</option>
