What is a general term for an organism with more than 4 legs?

multipedal

There is no generic term for something with multiple legs that specifically excludes organisms with 2, 3 or 4 legs. You either have 0, 1, or more than 1.

Polypod is defined as having many legs. From Oxford:

adjective

Zoology

Having many feet or similar appendages, especially denoting a phase of insect larval development characterized by a segmented abdomen with rudimentary or functional appendages.

The use does appear to have been extended to robots, where polypedal is also used.

Besides polypod that @Chris H suggested, there is also polyped (as an adjective), which means having many feet. However, it doesn't actually specify having more than four feet. I guess it would depend on whether you consider many to mean more than four feet for your purposes. An organism with many feet can be called a polyped (noun).

Myriapodous = having numerous legs.

This was a Crossword clue in today’s Age.

OED

Origin: **Formed within English, by derivation.

Etymology: < Myriapoda n. + -ous suffix.

1843 R. Owen Lect. Compar. Anat. Invertebr. Animals 201 In the Myriapodous insects..the principle of irrelative repetition prevails in the nervous system.

1998 Rec. Austral. Mus. 50 293 The myriapodous arthropod Maldybulakia Tesakov & Alekseev, 1998, was first described from the Lower Devonian (Pragian–Emsian) in central Kazakhstan.

Myriapoda, n. A group of arthropods comprising the centipedes, millipedes, pauropods, and symphylans, which have elongated bodies with numerous leg-bearing segments; (with plural agreement) such arthropods collectively.