As a noun iridescence

is the condition or state of being iridescent; exhibition of colors like those of the rainbow; a prismatic play of color.

As an adjective undefined is

lacking a definition or value.

As adjectives the difference between sustainable and undefined

is that sustainable is able to be sustained while undefined is lacking a definition or value.

As adjectives the difference between perceptive and undefined

is that perceptive is having or showing keenness of perception, insight, understanding, or intuition while undefined is lacking a definition or value.

As a noun downgrade

is a reduction of a rating, as a financial or credit rating.

As a verb downgrade

is to place lower in position.

As an adjective undefined is

lacking a definition or value.

As adjectives the difference between ungeometrical and undefined

is that ungeometrical is not geometrical while undefined is lacking a definition or value.

As a noun journalist

is journalist.

As an adjective undefined is

lacking a definition or value.

As adjectives the difference between poor and undefined

is that poor is with little or no possessions or money while undefined is lacking a definition or value.

As a noun poor

is (with "the") those who have little or no possessions or money, taken as a group.

As a verb distinguish

is to see someone or something as different from others.

As an adjective undefined is

lacking a definition or value.

As a noun homologation

is (organic chemistry) any reaction that converts a compound into the next member of a homologous series, usually by lengthening a carbon chain.

As an adjective undefined is

lacking a definition or value.

As a noun residue

is whatever remains after something else has been removed.

As an adjective undefined is

lacking a definition or value.