Definitions:

1. a reservation that is improved noun
   • I got an upgrade to first class when coach class was full
2. get better travel conditions verb
   • I upgraded to First Class when Coach Class was overbooked
3. give better travel conditions to verb
   • The airline upgraded me when I arrived late and Coach Class was full
4. the act of improving something (especially machinery) by raising it to a higher grade (as by adding or replacing components) noun
   • the power plant received a new upgrade
5. to improve what was old or outdated verb
   • I've upgraded my computer so I can run better software

Synonyms:

• raise
• rise