The sudden stunned silence that falls on a room after a person says something stupid, unfunny or offensive. Refers to the tumbleweed
featured in cowboy movies.
"...until Mrs Bush leant across to ask Condoleeza whether black men really did have bigger ones. The President broke the tumbleweed moment by declaring war on France."
The awkward silence that follows a remarkably dumb, over-the-top comment that nobody else in the room seems to understand, find funny or agree with. (Alluding to the "cartoon moments" in which a tumbleweed passes by in the dessert and all you can hear is the wind`s sound)
Person 1: Did you see that news about the floods in South America?
Person 2: Yeah, that was really funny. Anyway I think they totally had it coming.
Everybody else: .......................... (Tumbleweed moment)
A tumbleweed moment is when someone says something awkward and nobody says anything for some time.
Person 1: OMG I just got a pet dog, I love him so much!
Person 2: I know right, I love dogs too! They taste especially great in gravy.
Person 1: Um...
Person 3: What a tumbleweed moment.