Tongue twister
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 qiqinibs "a frog in water jumps", in which "q" is a sort of gulping sound.
The sign language equivalent of a tongue twister is called a finger fumbler.
For examples, see list of tongue twisters.