These are languages which do not have sufficiently strict typing to be included in the StaticallyTypedLanguages or DynamicallyTypedLanguages categories. These languages give programmers total flexibility in writing their programs, but mistakes in these programs could result in undefined behavior or undetected errors at runtime. Languages of this type tend to be low-level, with unrestricted access to memory. Programming in these languages is frequently done for necessity or compatibility reasons, not for speed (see LowLevelMyth).
Some untyped languages:
AssemblyLanguage (with the obvious exception of TypedAssemblyLanguage)