Marty was bummed after his flight was delayed. He wasn't going to arrive in Cancun in time to watch the parade.
Bill: Hey, Ted. Why are you so bummed these days?Ted: Hey, Bill. I'm bummed I failed my English test and now my parents won't let me go to Sandy's farewell party!
In Examples 1 & 2, Marty and Ted are bummed. They are a little sad and disappointed by their circumstances. However, the idiom to be bummed isn't usually used for serious situations.
This idiom was taken from LSI's book titled Speaking Transitions. This book is used to teach Level 4 Speaking classes at LSI schools. For more information please visit: www.languagesystems.com