Letdown (noun)

1. A disappointment.
2. A feeling of disappointment or discouragement.

Origin:

1860, from let down (v.).

Examples:

1. The concert was a letdown and not as good as expected.
2. The team had a letdown and lost the game.
3. The project was a letdown and did not meet expectations.
4. The game was a letdown after the team had been on a winning streak.
5. The letdown was palpable in the room after the announcement of the cancellation.