I think a decent rule of thumb is: for people it means skinny, for TFs it means birdlike leg joints (especially re. the knees).
AFAIK TF things like this usually get named after individual toys/characters, i.e. (Bulkhead Syndrome), other franchises (Pokeformers), and/or obvious descriptions (shellformer, Gold Plastic Syndrome), with the latter two often ending in -former.

Either way, I want that Starscream, and maybe Shockwave too.