Definition
The word for “bored”, in the sense of being uninterested and feeling tired, is gelangweilt in German. Its corresponding noun “boredom” is Langeweile — essentially a “long while” or “a long period of time”.
The word for “boring” is langweilig.
Likewise, the word for “interesting” is interessant and “interested” is interessiert. Just as with their bored/boring counterparts, these should not be confused with one another.
Examples
The phrase “I am bored.” can be expressed in three different ways:
Ich langweile mich.
Ich bin gelangweilt.
Ich habe Langeweile.
Note the differences:
Er ist gelangweilt. He is bored.
Er ist langweilig. He is boring.
Er ist interessiert. He is interested.
Er ist interessant. He is interesting.
Good to Know
“To be interested in (something)” is sich (für etwas) interessieren in German.
Ich interessiere mich für Autos. I am interested in cars.