A tongue-twister is a phrase in any language that is designed to challenge the speakers of proper articulation. Many tongue-twisters have two or three sequences of sounds, then the same sequences of sounds with some sounds exchanged, e.g. "she sells / sea shells".
Some tongue-twisters are specifically designed to cause the inadvertant pronunciation of a profanity if the speaker stumbles verbally.
Something that might be regarded as a type of tongue-twister is a shibboleth, that is, a phrase in a language that is difficult for someone who is not a native speaker of that language to say. An example is Georgian baqaqi ts'khalshi qiqinebs "a frog croaks in the water", in which "q" is a sort of gulping sound.
The sign language equivalent of a tongue twister is called a finger fumbler.
....og her er en side med noen tungetvinnere på diverse språk : http://www.wordiq.com/definition/List_of_tongue-twisters#German