Defunct means no longer existing or functioning. It refers to something that has ceased to exist or is no longer in operation. In this question, we are asked to select the word that gives the nearest meaning of "defunct" from the given options.

The options are:
a) Disused
b) Useless
c) Useable
d) Useful

A) Disused: This option means not being used or no longer being used. It is the correct answer to the question. When something is defunct, it is no longer in use or operation, similar to being disused.

B) Useless: This option means having no use or purpose, being of no practical value. Although it is similar in the sense that something defunct may no longer have any use, it does not directly convey the meaning of "defunct" as it implies a lack of usefulness, rather than non-functioning or non-existence.

C) Useable: This option means capable of being used or useful for a particular purpose. It is the opposite of "useless" and does not convey the meaning of "defunct". It implies that something is still functioning or can be used, whereas "defunct" implies the opposite.

D) Useful: This option means being able to be used for a practical purpose or producing a desired result. It is the opposite of "useless" but does not convey the meaning of "defunct". Something that is defunct is no longer useful or producing any results.

Therefore, the correct answer is option A) Disused as it best represents the meaning of "defunct" as something that is no longer in use or operation.