As adjectives the difference between optional and undefined

is that optional is not compulsory; left to personal choice; elective while undefined is lacking a definition or value.

As a noun organelle

is organelle.

As an adjective undefined is

lacking a definition or value.

As a noun subjectivity

is (singulare tantum) the state of being subjective.

As an adjective undefined is

lacking a definition or value.

As a noun skiff

is a small flat-bottomed open boat with a pointed bow and square stern or skiff can be (weather|nova scotia) a deep blanket of snow covering the ground.

As a verb skiff

is to navigate in a skiff.

As an adjective undefined is

lacking a definition or value.

As a noun recession

is recession.

As an adjective undefined is

lacking a definition or value.

As a noun alogia

is a general lack of additional, unprompted content in normal speech, a common symptom of schizophrenia.

As an adjective undefined is

lacking a definition or value.

As adjectives the difference between insidious and undefined

is that insidious is producing harm in a stealthy, often gradual, manner while undefined is lacking a definition or value.

As adjectives the difference between forbidden and undefined

is that forbidden is not allowed while undefined is lacking a definition or value.

As a verb forbidden

is .

As adjectives the difference between nonephemeral and undefined

is that nonephemeral is not ephemeral while undefined is lacking a definition or value.

As adjectives the difference between unattentive and undefined

is that unattentive is not attentive while undefined is lacking a definition or value.