Can I have a static lookup table *inside* my xsl stylesheet?

Something like

<xsl:stylesheet>

 <definitions>
  <term name="GMT">Greenwich Mean Time</term>
  <term name="MST">Mountain Standard Time</term>
 </definitions>

 <xsl:template>
  <xsl:value-of select="document()//definitions[@name='GMT']"/>
 </xsl:template>

Some corrections:
1. elements which don't belong to the XST namespace
are allowed as direct children of xsl:stylesheet as long
as they are put into another namespace
2. the stylesheet itself is adressed as document('')

<xsl:stylesheet  version="1.0"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
  xmlns:data="urn:some.urn"
  exclude-result-prefixes="data">

  <data:definitions>
    <term name="GMT">Greenwich Mean Time</term>
    <term name="MST">Mountain Standard Time</term>
  </data:definitions>

  <xsl:template>
    <xsl:value-of select="document('')/*/data:definitions[@name='GMT']"/>
  </xsl:template>
 ...