There is a big difference between hyperthreading and multithreading.
Rather, it depends on what you consider multithreading.
Normally you have time-sharing multitasking, in which processes may have many threads, and all threads "run" at the same time, yet the CPU still only deals with one thread each time slice and then context switches to the next thread. This is virtual thread-level parallelism. It could be called multithreading, since processes may still split execution into discrete threads.
In SMP enabled systems, you have true multithreading, in which two physical processors each simultaneously can execute threads, either belonging to the same or different processes. This is true thread-level parallelism. This is another type of multithreading.
In a hyperthreading system, you have a very similar idea to SMP, however you can not achieve true thread-level parallelism in most cases. That is, the CPU still only has one execution path, however in some cases another thread may share the unused resources along the path inside the CPU. This is a kind of hybrid true/virtual thread-level parallelism, since some threads can, more or less, run in parallel, and some cannot. This is also "sort of" multithreading.