Dissociate vs Undefined - What's the difference?

As a verb dissociate

is to make unrelated; to sever a connection; to separate.

lacking a definition or value.

To make unrelated; to sever a connection; to separate.

A number of group members wish to dissociate themselves from the majority.

To part; to stop associating.

After the big fight, the gang totally dissociated from each other.

(chemistry) To separate compounds into simpler component parts, usually by applying heat or through electrolysis.

We dissociated the lead iodide into its elements by heating

(chemistry) To undergo dissociation.

(psychology) To undergo dissociation.

Gerald checked himself into the hospital because he was dissociating .

* associate

* dissociation * dissociative

(wikipedia undefined) (-)

Lacking a definition or value.

(mathematics, computing) That does not have a meaning and is thus not assigned an interpretation.

The result of division by zero is undefined .

* defined