Arūpa (Template:Lang-Deva) means formless. It is the antonym for rūpa, and is used to refer to non-physical (i.e., non-material) subjects. It appears in Hinduism, such as in the description of Nirguna Brahman. It is also used in Buddhism.
Comparisons
Ether (akasha in Sanskrit) is somewhat arūpa, while classical elements are more rupa.[1]